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POURRA OF GEOLOGY
A Semi-Quarterly Magazine of Geology and Related Sciences
EDITORS T. C. CHAMBERLIN R. D. SALISBURY RAS Hee NROSEAMiRe Geographic Geology Liconomic Geology J. P. IDDINGS C. R. VAN HISE Petrology Pre-Cambrian Geology
W. H. HOLMES, Anxthropic Geology
ASSOCIATE EDITORS
SIR ARCHIBALD GEIKIE JOSEPH LE CONTE
Great Britain University of Calitornia H. ROSENBUSCH Cc. D. WALCOTT
Germany U.S. Geological Survey CHARLES BARROIS G. K. GILBERT
France Washington, D. C. ALBRECHT PENCK H. S. WILLIAMS
Austria Vale University HANS REUSCH J. C. BRANNER
Norway Leland Stanford University GERARD DE GEER I, (CG, IRUWSSISILIL,
Sweden University of Michigan. GEORGE M. DAWSON WILLIAM B. CLARK
Canada Johns Hopkins University
O. A. DERBY, Brazil
VOLUME any.
CHICAGO
Che BAnibversity of Chicago Press 1896
PRINTED AT
The University of Chicago Press
Cowments of VoLtome IV.
NUMBER I.
REVIEW OF THE GEOLOGICAL LITERATURE OF THE SOUTH AFRICAN RePpuBLic. S. F. Emmons = = = = = : = =
IGNEOUS INTRUSIONS IN THE NEIGHBORHOOD OF THE BLACK HILLS OF DaxoTa, Israel C. Russell - = = = - - - -
THE GEOLOGY oF NEW HAMPSHIRE. C. H. Hitchcock - - - NorTH AMERICAN GRAPTOLITES. R. R. Gurley - - - ; =
EDITORIALS = - = = 3 - é E i s z ‘
Reviews: The Hill Caves of Yucatan, by Henry C. Mercer (review by T. C. Chamberlin), 106 ; New Evidence of Glacial Man in Ohio, by Pro- fessor G, Frederick Wright (review by T. C. Chamberlin), 107 ; Fos- sil Sponges of the Flint Nodules in the Lower Cretaceous of Texas, by J. A, Merrill (review by T. Wayland Vaughan), 112; Thirteenth Annual Report of the State Geologist (New York), by James Hall (review by S. Weller), 116; Istidens foraminifer 1 Denmark og Hol- sten og deres betydning for studiet af istidens aflejringer, by Victor Madsen (review by J. A. Udden), 119; Om Lommalerans Alder, by N. O. Holst and Joh. Chr. Moberg (review by J. A. Udden), 123; Har det funnits mera ann en Istid i Sverige? by N. O. Holst, 124; Les Glaciers Pliocénes et Quaternaires de l’Auvergne, by M. Marcellin Boule (review by H. C. Cowles), 125; Neocene Mollusca of Texas, or Fossils from the Deep Wells at Galveston, by G. D. Harris (review by S. Weller), 126.
AuTHOoRS’ ABSTRACTS: Preglacial and Postglacial Valleys of the Cuya- hoga and Rocky Rivers, by Warren Upham, 127; A Needed Term in Petrography, by L. V. Pirsson, 128.
NUMBER II.
KAME AREAS IN WESTERN NEW YORK SOUTH OF JRONDEQUOIT AND Sopus Bays. H. L. Fairchild - E - = = = - -
A PRE-TERTIARY NEPHELINE-BEARING Rock. F. Bascom - - -
PETALOCRINUS MIRABILIS (N. SP.) AND A NEW AMERICAN Fauna. 5S. Weller and R. A. Davidson - - = = 2 P a : ili
PAGE
103
iv CONTENTS OF VOLOME TV:
REMARKS ON PETALODUS ALLEGHANIENSIS. Charles R. Eastman - - ON THE NATURE OF IGNEOUS INTRUSIONS. Israel C. Russell - - - STUDIES FOR STUDENTS: Deformation of Rocks. C.R. Van Hise - - EDITORIALS - - - - - - - - - - - -
REVIEWS: Age of the Second Terrace on the Ohio at Brilliant near Steuben- ville, by G. Frederick Wright (review by T. C. Chamberlin), 218. North American Fossil Crinoidea Camerata, by Charles Wachsmuth and Frank Springer (review by Charles R. Keyes), 221. En resa till norra ishafvet sommaren 1892 foretagen med understod af vegastipen- diet (A Journey to the Arctic Ocean during the Summer of 1892, made with the Aid of the Vega Stipend), by Axel Hamberg (review by J. A. Udden), 240; Paleontographia Italica. Memoire di Palzontologia, by Mario Canavari (review by J. P. S.), 242; The Soil: Its Nature, Relations and Fundamental Principles of Management, by F. H. King (review by J. C. B.}, 243.
AUTHORS’ ABSTRACTS: The Loess of Western Illinois and Southeastern Iowa, by Frank Leverett, 244; Possible Depth of Mining and Boring, by Alfred C. Lane, 244; The Soils of Texas, by E. T. Dumble, 245; The Yardley Fault and The Chalfont Rock, so-called, by Benjamin Smith Lyman, 245; Crystalline Limestones of the Northwestern Adirondack Region, by C. H. Smyth, jr., 246; U.S. Geologic Atlas, Folio 1, Livingston, Montana, 246; U.S. Geologic Atlas, Folio 3, Placerville, California, 248; U.S. Geologic Atlas, Folio 5, Sacra- mento, California, 250; U. S. Geologic Atlas, Folio 7, Pikes Peak, Colorado, 251; U.S. Geologic Atlas, Folio 9, Anthracite — Crested Butte, Colorado, 253.
NUMBER III.
THE MAGMATIC ALTERATION OF HORNBLENDE AND BIOTITE. Henry S. Washington - - - - - - - - - - ON THE ORIGIN OF THE CHOUTEAU FAUNA. Henry Shaler Williams — - NorRTH AMERICAN GRAPTOLITES. R. R. Gurley - - - - - STUDIES FOR STUDENTS: Deformation of Rocks. II. C.R.Van Hise - EDITORIAL - - - - - - - - - - - - REVIEWS: Geological Biology, an Introduction to the Geological History of Organisms, by H. S. Williams (review by S. Weller), 355; Cana- dian Fossil Insects, by S. H. Scudder (review by S. Weller), 360.
Summary of Current Pre-Cambrian North American Literature, by C. R. Van Hise, 362.
AuTHoRS’ ABSTRACTS: Origin of the Iowa Lead and Zinc Deposits, by A. G. Leonard, 373; The Gold-Silver Veins of Ophir, California, by W.
PAGE
174 176 195
214
257 283 291 312 354
CONTENTS OF VOLUME IV
Lindgren, 373; Ueber das Norian oder Oberlaurentian yon Canada, by Frank D. Adams, 374; Relations of the Granite and Porphyry Areas in Southeastern Missouri, by Chas. R. Keyes, 375; Syenite- gneiss (Leopard Rock) from the Apatite Region of Ottawa County, Canada, by C. H. Gordon, 377.
RECENT PUBLICATIONS - - = = = c = ; 2 =
NUMBER IV.
CLASSIFICATION OF MARINE TRIAS. James Perrin Smith - = = =
THE GEOLOGY OF THE LITTLE Rocky MouNTAINS. Walter Harvey Reed and Louis V. Pirsson - - - - . - - - -
SCHISTOSITY AND SLATY CLEAVAGE. George F. Becker - - - -
STUDIES FOR STUDENTS: Deformation of Rocks. III. C. R. Van Hise, 449; Large Scale Maps as Geographical Illustrations. W. M. Davis, 484.
EDITORIAL - - - - - - - - - - -
REVIEWS: Expedicion Cientifica al Popocatapetl, by Jose G. Aguilera and Ezequiel Ordoitez (review by Oliver C. Farrington), 516; Stratigraphy of Kansas Coal Measures, by Erasmus Haworth; Classification of the Upper Paleozoic Rocks of Central Kansas, by Chas. S. Prosser ; Permian System of Kansas, by F. W. Cragin (review by Chas. R. Keyes), 520; Wissenschaftliche Ergebnisse der Finnischen Expedi- tionen nach der Halbinsel Kola, by Dr. W. Ramsay and others (review by D. P. \N.), 526.
RECENT PUBLICATIONS : - - - = = < 2 - =
NUMBER V.
DECOMPOSITION OF ROCKs IN BRAZIL. Orville A. Derby - - -
ITALIAN PETROLOGICAL SKETCHES.—I. THE BOLSENA REGION. Henry S. Washington - - - - = = 2 8 E E 4
DRAINAGE MODIFICATIONS AND THEIR INTERPRETATION. Marius R. Campbell - - - : - = = z :
GLACIAL STUDIES IN GREENLAND. IX. T.C. Chamberlin - - - STUDIES FOR STUDENTS: Deformation of Rocks, IV. C.R. Van Hise - EDITORIAL - = - = = = = = = - E - Reviews: Greenland Ice Fields and Life in the North Atlantic, with a new discussion of the causes of the Ice age, by G. Frederick Wright and War- ren Upham (review by T. C. C.), 632; Ice Work, Present and Past, by
T. G. Bonney (review by T. C. C.), 636; General Relations of the Granitic Rocks in the Middle Atlantic Piedmont Plateau, by G. H.
PAGE
379
514
526
529
541
567 582 593 630
vi GONTEN DS (OF, VOLE OME TV,
Williams (review by H. F. Bain), 638; Sketch of the Geology of the San Francisco Peninsula, by Andrew C. Lawson (review by A. H. Purdue), 640.
ABSTRACTS: University Geological Survey of Kansas, Vol. 1,645; Till fragan om lommaleransalder, by Gerard de Geer, 646; Om strandliniens for- skjutning vid vara insjoar, by Gerard de Geer, 647; The Search for the North Pole, by Evelyn Briggs Baldwin, 649; lowa Geological Survey, Vol. V, 649; Monoclinic Pyroxenes of New York State, by Heinrich Ries, 651; Fifteenth Annual Report of the U.S. Geological Survey, 652; Notes Concerning a Peculiarly Marked Sedimentary Rock, by Dr. J. E. Talmage, 653.
RECENT PUBLICATIONS = 2 = 3 as = 5 2 s u
NUMBER VI.
DRAINAGE MODIFICATIONS AND THEIR INTERPRETATION. ee OL, CRITERIA FOR DETERMINING STREAM MODIFICATIONS. Marcus R. Campbell - : ° - Ser aie = - - - -
THE MONCHIQUITES OR ANALCITE GROUP OF IGNEOUS Rocks. L. V. Pirsson~ - - - - - - - - - - - -
THE QUEEN’S RIVER MORAINE IN RHODE ISLAND. J. B. Woodworth and C.F. Marbut - - = : = = = - = = -
STUDIES FOR STUDENTS: The Principles of Rock Weathering. George P. Merrill - = S = = - = - 2 2 - E
EDITORIALS - z E 2 : 3 . i z as Bi
REVIEWS: Great Valley of California, a Criticism of the Theory of Isostasy, by F. Leslie Ransome; British Geology, by T. Mellard Reade; Notes on the Gravity Determinations reported by Mr. G. R. Putnam, by Grove Karl Gilbert (review by Charles R. Keyes), 729; Text-Book of
Paleontology, Vol. I, Part 1, by Karl A. von Zittel, translated and -
edited by Charles R. Eastman (review by Charles R. Keyes), 734; Die Eruptivgesteine des Kristianiagebietes. II. Die Eruptionsfolge der triadischen Eruptivgesteine bei Predazzo in Siidtyrol, by Professor W. C. Brogger (review by F. L. Ransome), 738.
Summary of Current Pre-Cambrian North American Literature, by C. R. Van Hise, 744.
ABSTRACTS: Relation between Ice-Lobes south of the Driftless Area, by Frank R. Leverett, 757; The Production of Coal in 1894, by Edward W. Parker, 757; Merocrinus Salopie n. sp. and another Crinoid from the Middle Ordovician of West Shropshire, by F. A. Bather, 758; U. S. Geologic Atlas, Folio 10, Harper’s Ferry, Virginia and Mary- land, 758; Folio 2, Ringgold, Georgia and Tennessee, 760; Folio 4, Kingston, Tenn., 762; Folio 6, Chattanooga, Tenn., 764; Folio 8, Sewanee, Tenn., 766.
PAGE
654
657
679
691
704 725
CONTENTS OF VOLUME IV
NUMBER VII.
SALIENT POINTS CONCERNING THE GLACIAL GEOLOGY OF NORTH GREEN- LAND. Rollin D. Salisbury - - - - - - - : GENEsIs OF LAKE AGAssiIz. J. Burr Tyrrell - - - - = LACCOLITES IN SOUTHEASTERN CoLorapo. G. K. Gilbert - - - ITALIAN PETROLOGICAL SKETCHES, II. THE VITERBO REGION. Henry S. Washington - . - - - - - = : = STUDIES FOR STUDENTS: The Principles of Rock Weathering (concluded). George P. Merrill - - - - - - - = = EDITORIAL - - - - - - - = - 2 = 2 REVIEWS AND ABSTRACTS: Physical Features of Missouri, by Curtis Fletcher Marbut (review by R. D. S.), 877; Geological Atlas of the United
States, Folio 18, 878; Sixteenth Annual Report of the U. S. Geol. Survey, Charles D. Walcott, Director, 879.
NUMBER VIII.
AGE OF THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. WITH A REPORT ON THE FLORA OF INDEPENDENCE HILL. Waldemar Lind- gren - - - - = = = - - - - =
ANORTHOSITES OF THE RAINY LAKE REGION. A. P. Coleman - - - MECHANICS OF GLACIERS. I. Harry Fielding Reid - - - - > LOEss IN THE WISCONSIN DRIFT FORMATION. Rollin D. Salisbury - -
GEOLOGY OF CHIAPAS, TABASCO AND THE PENINSULA OF YUCATAN. Carlos Sapper. Translated by C. Joaquina Maury and G. D. Harris
STUDIES FOR STUDENTS: Stratified Drift. Rollin D. Salisbury - - EDITORIAL - - - - 2 = = S 5 a .
REviEws: Elements of Geology, by Joseph Le Conte (review by T. C. C.), 972; The Oldest Fossiliferous Beds of the Amazon Region, by Fried- erich Katzer (review by J. C. Branner), 975; The Formation of the Quaternary Deposits of Missouri, by J. E. Todd (review by T. C. C.), 976; Der Elaolithsyenit der Serra de Monchique, seine Gang- und Contactgesteine, by K. v. Kraatz-Koschlan and V. Hackman (review by F. L. Ransome), 977; Geological Survey of Canada (review by H. F. Bain), 979; Proceedings of the Indiana Academy of Science, 1895, Geological Subjects (review by J. C. B.), 981; Areal Geology of Mis- souri (notice by H. F. B.), 982; Om Kvartara Nivaforandringar vid Finska viken, by Gerard de Geer (review by J. A. Udden), 982.
Vil
881 907 gI2 929
938 948 971
WORN AL OF GEOLOGY
JANUARY-FEBRUARY, 1896.
REVIEW OF Tih GEOLOGICAL LIZERATURE, OF DHE SOULE AE RICAN REP UBELES
Topography.—The most characteristic features of South African topography appear to be its table lands. The interior of the country is in great measure a vast extent of high plateaux —the Hooge Veldt—which, though grassy, are practically tree- less and present much the same aridity and desolateness of aspect as many of our western mesas. Along the coast, especi- ally on the south and east, is a belt of country of a generally lower level, which is more rugged and broken, but even here plateaux occur, sometimes on the very coast, as, for instance, the well-known Table Mountain near Capetown.
As one leaves the coast to go into the interior the country becomes more mountainous, often rising into considerable ranges like the Drakensberg range, which runs parallel to the southeast coast and has peaks rising to elevations of 10,000 feet or more.’
* Read before the Geological Society of Washington, November 13, 1895.
2 AUTHORITIES CONSULTED IN THE PREPARATION OF THE PRESENT PAPER.
1888. A. H. GREEN: Geology and Physical Geography of the Cape Colony, Quar. Jour., Vol. 44, pp. 239-270.
1889. A.SCHENCK: Vorkommen des Goldes in Transvaal. Zeitsch. d. Deut. Geol. Gesellsch, Band XLI., pp. 573-581.
1890. W.H. FuRLONGE: Geology of the De Kaap Gold Fields. Trans. Amer. Inst. Mg. Engrs, Vol. XVIII., pp. 334-348.
1891. W.H.PENNING: A Contribution to the Geology of the Southern Transvaal. Quar. Jour., Vol. XLVII., pp. 451-463.
Vion. LV; No. 2. I
2 S. &. EMMONS
As a rule, however, these mountains do not reach above the level of the high plateau, which forms an abrupt escarpment near or behind them, and slopes away gently toward the interior. Thus the drainage of the plateau region from within 100 miles or less of the east coast flows westward through the various tributaries of the Orange River into the Atlantic Ocean. The country is yet too new and too little explored by geologists to afford certain data for a physical description founded on its previous geological history, such as would be given by a physical geographer of the present school like our William M. Davis, but it is evident that the region presents a most interesting and fruitful field for this line of study. From what has already been written it is easy to make the preliminary deduction that the coast belt, like the east coast of Lower California, shows an older topography that has been exposed by the denudation of the more recent formations that constitute the plateau regions.
Development.—The general advance of exploration, coloniza- tion and civilization has moved eastward and northward, instead of westward as with us. From the older settlements of the Cape
1891. L. DE LauNnAy: Les mines d’or du Transvaal. Ann. des Mines, Serie 8 Tome XIX., p. 102.
1892. Watcor Gipson: Geology of Gold-bearing and Associated Rocks of the Southern Transvaal. Quar. Jour., XLVIIIL., pp. 404-437.
_ 1894. G. A. F. MOLENGRAAF: Geologie der Umgegend der Gold-felder in Siid- Afrika. Neues Jahrb. f. Miner, etc., Beilage Bd. IX., p. 175.
1894. BERGRATH SCHMEISSER: Ueber Vorkommen und Gewinnung der nutz- baren Mineralien in den Stid-Afrikanischen Republik. D. Reimer, Berlin, 1894.
1894. A. PELIKAN: Goldfiihrendes Conglomerat von Witwatersrand. K. K. Reichsanstalt, No. 16, December 18, 1894, p. 421.
1895. F.H. HatcuH and J. A. CHALMERS: Gold Mines of the Rand. Mac- millan & Co., New York and London, 1895.
Among geologists who have written in earlier times upon the geology of the southern portion of Africa, but not directly upon the South African republic, may be mentioned A. G. BAIN (Quar. Jour., 1845), R. N. RuBIDGE (Quar. Jour., 1854-6), ANDREW WYLEY (1857-8), G. W. Stow and C. L. GRIEsBACH (Quar. Jour., 1870), E. J. DuNN, On Diamonds (Ouar. Jour., 1874, 1877 and 1881), W. H. PENNING, On Coal (Quar. Jour., 1884), MOULLE (Ann. des Mines, 1885), E. COHEN (Neu. Jahrb., 1887).
The only geological map of South Africa is one made by E. J. Dunn, as Geologist of the Government of Cape Colony, and published in 1887. This covers most of the South African republic, but has no topographic base, and its geological outlines in the more northern portions are very sketchy.
GEOLOGY Oh THE SOUTH APRICAN REPUBLIC 3
Colony it spread eastward, then northward along the coast line, and later the search for useful minerals led people into the desolate interior. Coal was the first desideratum, and that was found in the beds of the first high plateau, or Karoo region. Further
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Note.—The accompanying sketch map shows roughly the political divisions of the southern portion of the African Continent, the location of the principal mining towns and ports, and the main railroad lines.
advances into this region led to the discovery of the diamond deposits, and the foundation of the Orange Free State. Following northwestward along the coast of the Indian Ocean, through Natal and Zululand, exploration next developed gold- bearing quartz veins in the valleys of the Crocodile River which debouches into Delagoa Bay, and of the Oliphant’s and other tributaries of the Limpopo River which forms the semi-circular
4 S. &. EWMONS
northern boundary of the South African republic. This state is
more commonly known as the Transvaal, because it lies beyond the Vaal River, the northern and main fork of the Orange River, which divides the South African republic from thé Orange Free Stare:
These first discovered gold fields now comprise many districts, the most prominent of which are the Lydenburg on the north, and the De Kaap and Komati on the south of the Crocodile River. Furlonge describes this region in the following words: ‘A large plateau stretches from east to west across the Transvaal, which is called the ‘High Veldt.’ It is generally level or gently rolling, -and has an average elevation of 6000 feet above the sea; it is destitute of timber, and in fact greatly resembles the western prairies of North America, and rock outcrops are not common. It terminates very abruptly to the east and northeast, the descent of 2000 to 3000 feet into the mountainous country that occupies its borders being made in a very short distance. These mount- ains extend in an easterly direction for a distance of forty miles, when they again terminate, very abruptly, in an apparently flat region composed of marshes and sandy plains, sloping gently but regularly to the shores of the Indian Ocean, a distance of about 100 miles.”
It was the gold fever, resulting from the rich discoveries in the De Kaap district that started prospecting in the spring of 1886, and caused the unexpected discovery of gold in fair ‘quantity and of great extent in the Witwatersrand (white water range) at the northern end of the great plateau of the Orange Free State and thirty miles south of Pretoria. Toward the end ‘of the same year the township of Johannesburg, now a city of 30,000 inhabitants, was laid out and lots sold to the amount of #13,000. Shares were quoted on the Johannesburg exchange in June 1887, and by November of the same year sixty-eight com- panies, with a nominal capital of 43,000,000 had been formed. A boom soon set in, which lasted till the end of 1889, when it burst, and the reaction continued for several years, but the increasing output of gold and augmentation of dividends in 1892
GEOLOGY OF THE SOUTH AFRICAN REPUBLIC 5.
and 1893 called the attention of outside capital to the mines again. In 1894 the Transvaal furnished one-fifth of the total gold product of the world, and was only exceeded among indi- vidual nations by the United States and Australia.
GEOLOGY.
The geological formations of South Africa are grouped by most geologists under the following four heads given in descend- ing order: (1) recent deposits, (2) Karoo formation, (3) Cape formation, (4) Primary formation.
Recent deposits —There is apparently no evidence of recent glacial action inSouth Africa. Dunn, in his early descriptions of the diamond deposits, attributed a glacial origin to certain bowlders observed near the Kimberley district, but afterwards withdrew this explanation of their origin as untenable. Furlonge says of the De Kaap region: ‘I have diligently searched for, but failed to find, evidences of glacial action, phenomena with which I happen to be very familiar from my residence in the Lake Superior district and the country north of it.” Other geologists. do not refer directly to the question, but all note the great extent of what they call laterite,t a formation which appears to result from the surface decomposition of rock-in-place, and to be similar to that found in the Appalachian region of the United States south of the limits of glaciation. This surface disintegra- tion is so deep and so widespread that outcrops are few and prospecting is thereby rendered difficult. While placer gravels. are infrequent and of limited extent, according to Schenck, gold is obtained by hydraulic washing of the laterite (or saprolite) of diabase beds and of surface flows covering the Cape forma- tion in the Lydenburg district, north of the Crocodile River. Furlonge, in his description of the De Kaap region, remarks on the large areas of decomposed granite in flat places and natural
*G. F. Becker proposes the term saprolite (from campés = rotten) for decomposed rock in place, objecting to the use of /a/erite, because in its original sense it had a lithological signification, and applies in part to transported material. Gold-fields of
the Appalachians, p. 43. Sixteenth Ann. Report Director U.S. Geol. Survey, Wash. , 1895.
6 S. &. EMMONS
drainage channels, whose decay he ascribes to the agency of meteoric waters remaining long in contact with the rock. The area on which the town of Barberton is situated is sixteen by eight- een miles in extent. Throughout these areas are what are called ‘““Tongas,” that is water-washes, with intricate drainage channels and perpendicular walls, not unlike the Bad-land topography of the West. The depth of this decomposition may reach 200 feet, while on the steep slopes of adjoining hills, and in bowlders rolled down onto the surface, the granite is hard and undecom- posed. The same decay is found in other feldspathic rocks.
Primary formation.—Under this head are included granites, and a series of schists called by Schenck the Swasi-schists, because of their abundance in Swasiland to the south and east of the De Kaap basin.
The granite is described by Molengraaf as consisting of micro- cline granite and of tonalite (plagioclase granite), muscovite being developed in the former as an alteration product of feldspar. Furlonge remarks on its light color and the absence of dark minerals in the De Kaap district. I find no explicit statement of the relative age of granite and schists, but Molengraaf says the schists rest upon the granite, and Schmeisser describes them as dipping away from it in three directions. For the most part these schists appear to be compressed into close folds and stand at steep angles, but in some cases they occupy a nearly horizontal position. While classed under a single head, it does not appear impossible that they may belong to two distinct series of rocks. According to Molengraaf they consist mostly of quartz-sericite and actinolite schists, and in places of conglomerates and sand- stones, also carrying sericite. Schmeisser describes them as in part metamorphosed beds of sedimentary origin, such as slates, quartzites and magnetite-quartz (calico) rock, but to a much greater extent of metamorphosed schists with greenstone dikes and sheets, the latter altered into hornblendic, chloritic and ser- pentinous schists. Molengraaf speaks of quartz-porphyry dikes in the schists around the granite. Schmeisser says gold-bearing veins occur wherever the Swasi formation is developed. They
GEOLOGY OF THE SOUTH AFRICAN REPUBLIC i
occur also to a considerable extent in the granite. Schenck con- siders that the quartz veins are intimately connected in most cases with interbedded sheets of greenstone, sometimes altered into schists, and that the greenstone ‘“‘appears to be the mother- rock proper of the gold.” They appear to resemble the gold veins of the Appalachians in that they are mostly parallel in dip and strike with the stratification (foliation?) planes, or cross them at a slight angle, and are nevertheless true fractures and often contain fragments of the country rock. Furlonge speaks of quartzite-like bands, which, resisting erosion, stand out on the surface in ridges and are called ‘“‘bars.”’ He considers them to be the result of silicic replacement, and says the principal gold deposits are found in or near these bars, but always in the prox- imity of some eruptive rock. Often instead of gold they carry deposits of iron oxide of great extent. The gangue of the veins is quartz, and, besides gold, much iron pyrites, some sulphides of copper, antimony, arsenic, lead and zinc occur.
The rocks of this formation stretch northward over 80 kilo- meters from the steep descent of the Drakensberg, along the eastern border of the high plateau, forming the Murchison range, and constitute the country rock of the De Kaap, Komati, Selati, Little Letaba and Smitsdorp districts. They also occur between Pretoria and Johannesburg. They are considered to be of Silurian age, partly from indistinct fossils remains, but more from stratigraphic correlation with beds underlying uncomform- ably the Cape sandstones in the Cape Colony, which have been determined to correspond most nearly to the European Silurian.
The Cape formation, so-called because supposed to correspond in age with the Cape sandstones of the Cape Colony, overlies uncomformably the Swasi-schists, and is in turn unconformably overlaid by the beds of the Karoo formation. It contains the gold-bearing conglomerates. Its beds are sometimes upturned, even quite steeply, but are not contorted, compressed or dynamo- metamorphosed to such an extent as are the Swasi-schists. No fossils have yet been found in its beds, but from its relative posi- tion, it is supposed to be either Devonian or Lower Carboniferous.
8 S. &. EMMONS
As the most important formation, its description will be given last.
Karoo formation.—Under this head are included a great series of beds, generally occupying a nearly horizontal position, which form the great central plateau or High Veldt of the Orange Free State, and extend into Natal on the east and Cape Colony on the south, leaving a comparatively narrow belt of upturned older rocks between their bluffs and the ocean. Its several subdivis- ions are variously named and classified in different places and by different writers. Those most commonly adopted are in descend- ing order:
Volcanic.
Cave sandstones. Red beds. Molteno beds.
\ Karoo beds. | Kimberly beds.
Ecca beds. Dwyka conglomerate.
Stormberg beds,
Beaufort beds,
Ecca beds,
The beds of the Karoo formation consist mainly of argilla- ceous, siliceous, and marly slates and sandstones, with a few lime- stones; they are generally much softer than corresponding rocks of the Cape formation, and often of variegated colors; the coal- bearing rocks are generally coarse-grained, light-colored sand- stones. The two lower of the above general divisions contain a Glossopteris flora (of the fern family) and are hence supposed to be as old as Triassic, and possibly Permian or upper Carbon- iferous in part. According to Hatch the coal seams are confined to the Molteno beds of the upper division, but Schmeisser, from the finding of Glossopteris remains, considers that some of the coal beds belong to the earlier rocks. The formation is traversed by dikes and sheets of greenstone and other eruptive rocks, especially the middle division.
It is in volcanic necks cutting the Kimberley shales that the diamonds occur, and, as early as 1881, Dunn suggested that they
GEOLOGY OF THE SOUTH AFRICAN REPUBLIC 9
were formed from the carbon in the shale through the agency of the intruded eruptive rocks.
Near the Witwatersrand the coal-bearing beds transgress horizontally over the upturned edges of the auriferous conglom- erates, and coal mines are worked at Bocksburg, Brakspan, Oli- fants River and other points within 12 to 20 miles of Johannes- burg. The coals are gas, coking, blacksmith and steam coals, all varieties being sometimes found ina single district. Beds up to 20 feet in thickness occur. Dunn speaks of an anthra- cite vein intersecting the Karoo beds vertically at Buffel’s Kloof in Cambedoo. Semi-anthracites are found, according to Schmeis- ser, in Bocksburg and Brakspan, which have a high percentage of ash. The ash from that of the former place, tested by Pro- fessor Stelzner, yielded to the assay $4.50 per ton in gold.
Remains of Labyrinthodonts (amphibia), and Dicynodont (few-toothed) and Oudenodont (toothless) reptiles from these beds have been described by Owen and Huxley. Both Equisete and Glossopteris occur inthe lower Karoo beds, according to Dunn. This peculiar fauna, and more particularly the Glossopteris flora, which apparently was only developed in the southern hemisphere, has called the attention of paleontologists especially to these beds. Schenck says that the fossil flora of South Africa, especially the characteristic 7innfeldia odontopteroides, stands in connection with that of the Argentine republic in South America, with the Rads- chmahal beds of India, the Hawkesbury and others of Australia, and those in the Jerusalem basin of Tasmania.
In most of these regions the base of the coal-bearing beds, in which this peculiar flora has so suddenly replaced that which in other countries characterizes the Carboniferous formation, consists of a conglomerate carrying peculiarly large, angular rock fragments. These features have seemed to many geologists to indi- cate the former presence of asouthern ice-sheet. On Dunn’s geolog- ical map the Dwyka conglomerate, which constitutes the lowest member of the Karoo formation, is called “glacial conglomerate.” Some earlier geologists, seeing it probably at different exposures, have called it claystone porphyry, others trap-conglomerate.
10 S. &. EMMONS
A. H. Green, who visited South Africa in 1882 for the pur- pose of examining the coal-bearing formations, speaks of it as a great mass of breccia and conglomerate, in which the fragments are largely granite with some quartzite of varying character and very coarse-grained in places. He considers the volcanic origin that had been suggested for it by no means certain, and remarks that the size and regularity of the pebbles suggest the action of ice and that some of the pebbles observed by him had scratches resembling glacial scratches. On weighing the evidence, how- ever, he concludes that it was a coarse shingle formed along a receding shore line.
He considers that there is a great unconformity between the Ecca beds and the overlying Kimberley shales, which he observed at one point overlapping the upturned edges of the former; he thought to recognize a basement conglomerate at the bottom of the Kimberley shales, which might have been confounded with the Dwyka conglomerate. He is inclined to regard the Karoo formation above the Ecca beds as of fresh water origin. Others have regarded the fossil evidence as in favor of a lacustrine origin for the whole series.
Cape formation.—The beds included under this head are inter- mediate in lithological character and in degree of deformation, as well as in stratigraphical position, between the Swasi-schists and the Karoo formation. They consist of sandstones, con- glomerates and shales, and in some regions of dolomitic lime- stones. As yet they have proved entirely barren of fossils. They extend over the southern, middle and western parts of the Transvaal. According to Hatch the long range of the Drakens- berg consists of these beds, and thus they probably extend to the Cape Colony where they are represented by the Table mountain sandstones and the shales, sandstones and quartzites of the Bokkeveldt beds. The age of the latter by fossil evidence most nearly corresponds to the European Devonian or Lower Carboniferous.
Within this formation name are comprised several series of rocks of very great aggregate thickness, with regard to whose
GEOLOGY OF THE SOUTH AFRICAN REPUBLIC II
relations to each other there is some difference of opinion among geologists. They may be separated into three groups.
1. Zhe Quartzite and Shale group of Gibson (Magaliesberg beds of Penning) underlying the auriferous conglomerates north of Johannesburg, and considered by Gibson to belong to the same series, though separated by a fault, which Molengraaf holds to be an unconformity.
2. The great series of auriferous conglomerates.
3. A series of Jdlue dolomites, alternating with siliceous or cherty beds. Those which occur in the Malmani district, to the west of Johannesburg, Molengraaf considers to be the upper
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Section across Rand.
part of the Cape formation, while immediately north of Johannes- burg similar dolomites underlie a series of quartzite and shales, which Schenck considers to correspond to those directly beneath the auriferous conglomerates. These dolomites have a wide distribution in the Western Transvaal and extend into Bechuana land.
The general relations of these beds is shown in a section given by Hatch, which is apparently drawn to scale, and extends from the Magaliesberg on the north, through Johannesburg, to the Black reef beds onthe south, a length of over twenty miles. On the line of this section immediately to the north of Johannes- burg, are the quartzites and shales, the former standing out as east and west ridges between shale valleys. They have a steep dip to the south, and are succeeded to the north by granite and schists, supposed to correspond to the Swasi-schists. To the north of the granite, and dipping northward away from it, are the dolomitic limestones of the Kalkheuvel range; beyond these again, still dipping north, is a series of quartzites and shales
I2 S. fF. EMMONS
forming the Witwatersberg and Magaliesberg ranges, which are supposed to correspond with these on the south side of the anticline, though not altogether similar lithologically. If, as Molengraaf maintains, the limestones are the Malmani dolo- mites, and belong above the conglomerates, the latter must be faulted down on the north side of the granite, and not appear at alll at the surface.
Returning again to Johannesburg and following the section line southward, there appear, resting on the quartzites and shales and apparently conformable with them (Gibson thinks they are only separated by a fault, but Molengraaf thinks there is an unconformity) a thick series of reddish sandstones with some shale, which enclose gold-bearing conglomerate beds of vary- - ing thickness, and form a flat, rolling country sloping gently south. These dip steeply at the outcrop but shallow in dip to the southward, and in a few miles are capped by a body of eruptive rocks, called by Hatch, in one place, ‘“‘a hard, fine-grained greenstone or melaphyr”’ and in another ‘an overflow of igneous rock of basaltic composition, known as the Klipriversberg amygdaloid.” Molengraaf speaks of it as an overflow of diabase and melaphyr amygdaloid with porphyrite, varying in thickness from 400 meters south of Johannesburg to 900 meters near Klerksdorp. This forms the hills called the Eagle’s Nest.
Upon the amygdaloid rests a series of shales, quartzitic sand- stones, and gold-bearing conglomerates which he calls the Boschrand (wooded mountains), but which are more commonly known as the Black reef series, because of a black seam which forms its footwall. This series jlolengraaf considers younger than the lower sediments and than the igneous rocks, but Gibson considers the intrusion of the igneous rocks to have been the latest phase. Hatch, to prove that they were deposited uncon- formably on the older conglomerates, adduces the facts (1) that they are nearly flat (10° against 45° to 80° dip of the lower beds), (2) that followed eastward they overlap the older series, (3) that they occasionally contain rolled fragments of the older conglomerates. The total thickness of this southerly dipping
GEOLOGY (OF THE SOGUTH ARRICAN REPUBLIC 13
series of sandstones and conglomerates, neglecting possible reduplication by faulting, is given as 17,000 to 18,000 feet. Schmeisser enumerates in this series some seventy beds of conglomerates, of which by no means all contain gold, and of those that do, comparatively few have enough to pay for work- ing, or are payable, as the South African phrase is. They are generally divided into groups or series of reefs, of which Hatch gives four in descending order beneath the Black reef series, viz., the Elsburg series: the Kimberley series: the Livingstone and Bird series: the Main reef series. The latter is that upon which the principal mines are working today. Beneath the Main reef series is the Dupreez or Rietfontein series, two and one-half miles north of Johannesburg, which has only been traced 10,000 feet along its strike, whereas the Main reef series has been traced more or less continuously for forty-five miles on the strike. Across the strike from the Dupreez outcrops to those of the Black reef series, is eight to ten miles.
As shown by the underground workings these gold-bearing beds are traversed by dikes and sheets of greenstone and con- siderably faulted.
Twenty-five miles south of Johannesburg, in the Heidelberg region, they are working on a series of a similar conglomerates, which dip 30° to the northward, and are assumed to belong to the south side of a syncline. It has not been possible, however, to correlate the Heidelberg and neighboring Nigel series with those outcropping in the Johannesburg region. Going eastward, on the strike both these and the southerly dipping beds pass within a few miles under the horizontal coal beds of the Karoo formation. The Johannesburg series have been proved under these beds by borings, and are assumed to curve round to the southwestward and find their continuation in the Nigel and Heidelberg fields. To the westward again the Johannesburg beds, at a distance of fifteen to twenty miles from the city, bend to the southwest, toward Potchefstrom and Klerksdorp where similar conglomerates outcrop. The outcrops thus form a sort of horseshoe curve. It is naturally a matter of great importance
14 S. &. EMMONS
to determine accurately the structure of the middle of this basin, where the surface is marshy or shows only outcrops of igneous rocks, and upon this subject much has been written.
Near Johannesburg the dip of the beds is generally 45° to 80° at the outcrop, though in a few instances not over 25°. This inclination decreases with depth, quite rapidly though with no uniformity, and at vertical depths of 500 to 1000 feet, it has usually become 30° or less; the borings show a probable angle as low as 12° at greater depths. Should this decrease continue _with sufficient rapidity, the whole basin, even at its deepest part, might be within the limits of profitable mining. Gibson, who is inclined to extreme views in regard to structure indications, says that the surface of the foot and hanging walls of the “reefs” or “bankets”’ are smooth and polished; the pebbles flattened, and sometimes completely shattered; the cementing material decidedly schist-like and squeezed in and out around the pebbles. He remarks further that the conglomerate beds are generally found to decrease in number as greater depth is reached. All these facts he regards as evidence of strong compressive move- ment combind with overthrust faulting. The apparent rapid decrease of angle of dip in depth he seems to think due to repetition by reversed faulting and he hence opposes the theory of a simple basin structure. The igneous rocks he regards as much later than the conglomerates, and probably later than the movement of compression, since the diorite intrusions show no effects of it.
Molengraaf, on the other hand, does not consider that there is any considerable folding in these beds, and thinks Gibson’s proof of overthrust faulting weak. He admits that both strike and dip faults are common, and that there are evidences of movements within the beds; he considers that these result from thrust faults with movement from north to south instead of from south to north as Gibson maintains. The rapid shallowing of the dip he thinks easily explained if the steep upturning of the beds around the rim of the basin is considered due to dragging of the strata over each other.
GEOLOGY OF THE SOUTH AFRICAN REPUBLIC is
The facts presented by Hatch, who devotes much less con- sideration to geological than to economic questions, lead one to conclude that there is one large and several smaller synclinal basins, none of which can be fully traced on the surface, and which are undoubtedly much broken by dynamic movements which have been accompanied by the intrusion of igneous rocks, mostly on the fault planes, but to a certain extent as intrusive sheets and laccolites. It seems not unlikely that the apparent basin structure indicated by outcrops, will be found to be much broken in depth by these igneous intrusions.
The auriferous conglomerates of the Rand—The area within which is the principal development of auriferous conglomerates is estimated at 2000 square miles. Gold deposits occur also in other beds assumed to belong to the Cape formation, notably in the dolomites of the Malmani district, as vertical quartz veins, and in the sandstones of the Lydenburg district, which rest on dolomites. None of these have yet assumed any considerable economic importance, however, and it is the area called for short the “Rand” that produces over nine-tenths of the South African gold.
In this area, though gold is found in most all of the several reef series enumerated above, it is rarely in paying quantities out- side of the Main reef series, upon which most of the mines near Johannesburg are working. In this series are several beds of conglomerate known respectively as the north, main, middle, and south reefs, and main and south reef leaders (this name is given to thin beds of conglomerate) not more than two or three of which are usually productive in the same mine. Schmeisser says the tenor in gold varies inversely with the thickness of the beds, and in many mines the principal values are obtained from the main reef leader, which averages only 15 inches in thickness while some of the reefs average six feet. Although there is con- siderable variation in the richness of the different beds, and of the same beds from one point to another, yet taking the district as a whole the gold seems to be distributed with remarkable uni- formity, as compared with other mining districts. Schmeisser
16 S. f. EMMONS
estimates $15.00 per ton as the average tenor of the ore mined throughout the whole district. Hatch puts it at $10.00, or half an ounce.
The central district of the Rand, on the Johannesburg side of the basin where the greatest concentration of mines exists at — present, is 1144 mileslong. The workings of these mines extend now to a depth of 800-900 feet in the case of those which started from the outcrop, while deep-level mines, or those which do not own the outcrop, are down as far as 2000 feet, in each case reck- oned on the dip. Drill holes sunk at various points in this extent, to vertical depths of between 2000 and 3000 feet, have proved the gold bearing conglomerates to distances of up to 8000 feet from the outcrop, and found, for the points thus tested, about the same average tenor in gold as higher up, with similar varia- tions from point to point.
The conglomerate beds and the sandstone which enclose them have a reddish tinge near the surface which is due to the oxida- tion of the finely divided iron, but in depth have the greenish or bluish-gray color common to rocks containing sulphides of iron. The conglomerate beds vary in thickness from a few inches up to six or more feet, and the pebbles of which they are com- posed from the size of a pea to that of a hen’s egg or even larger. These pebbles are generally smooth and well rounded, some- times flattened and not infrequently cracked and fissured; angu- lar pebbles are also found. They are mostly composed of white or smoky quartz; quartzite is also mentioned as a constituent. Gibson speaks of pebbles of a yellowish talcose material, like hardened clay, which may be altered igneous rocks. The cement consists mostly of small quartz fragments, and abundant but irreg- ularly distributed pyrite grains. Under the microscope it is seen to contain, beside quartz and gold, pyrite, magnetite, zircon. rutile, muscovite and chlorite, the last two minerals and some of the quartz being of secondary origin. The gold, which occurs almost exclusively in the cement, is generally invisible to the naked eye. When it does occur in the pebbles it is found in the delicate cracks or fissures associated with quartz which appears
GEOLOGY OF THE SOUTH AFRICAN REPUBLIC 17
to be secondary. Gold is sometimes found also in the sand- stones between the reefs.
Numerous dikes and some intrusive sheets traverse the beds ; the intrusive rocks are generally basic; diabase, olivine and bronzite-diabase, gabbro and olivine-norite being among the vari- eties recognized. The dikes generally follow fault planes. The faults, which are quite frequent, are both dip, strike and reversed faults. Quartz veins are said to cross the gold-bearing beds, and at the intersection the quartz becomes quite rich.
Origin of the gold—¥rom the very earliest discovery of these deposits the question as to how the gold came to be distributed in such quantities over such great areas and in so many different beds has been one that has occupied the attention of all geolo- gists who have visited the region. Probably the largest number, certainly among the earlier observers, have considered that the gold, like the pebbles of which the beds consist, results from the degradation and concentration by sea waves of material from an ancient landmass of Swasi-schists. They have seen in the quartz of the pebbles a resembiance to that of the veins which are so abundant in these rocks in the De Kaap and other outlying dis- tricts. A few have held that the gold was chemically deposited from the waters of the ocean; and another, and in late years an increasing, number believe that it has been deposited from ascend- ing or descending thermal solutions.
Schmeisser brought back specimens of the conglomerate ore from six of the principal mines of the Rand, which were sub- mitted to Dr. Koch for microscopical examination. The main results of this examination are as follows:
The pyrite shows the effects of wear in rounded edges, etc., and also occurs within the quartz pebbles; hence it is undoubt- edly of primary origin. The same is true of the magnetite and zircon. The rutile is, however, not original, and the muscovite and chlorite are evidently formed from the alteration of other minerals. Secondary quartz occurs both in the matrix and filling the cracks in the pebbles that result from dynamic action; it con- tains fewer inclusions than the primary quartz. The gold con-
me S. F. EMMONS
tained in the specimens (eight in number) that he examined is of secondary formation and not placer gold, for the following reasons:
1. It occurs either in microscopic crystals or in aggregates of angular form. Rounded and polished grains are altogether wanting.
2. It is not observed as inclusions in the quartz pebbles, but is confined to shattered zones and fissures filled with secondary quartz.
3. In the matrix, the gold is aggregated with pyrite grains, for the most part forming deposits on the outside of them, filling cracks and bays in them, and sometimes nearly enclosing them. It is noticeable, moreover, that the gold is connected only with grains of pyrite that have been separated from their matrix. The pyrite that is still enclosed in quartz pebbles is free from gold.
In conclusion he says: ‘‘ Whether the above observations on the occurrence of native gold can be considered of universal application, or whether they only fit local phenomena must remain undecided for the present and can only be finally deter- mined by the investigation of more extensive and complete material than was submitted to me.”
Pelikan, on the other hand, from the examination of five speci- mens from, in part, the same mines, brought back to Vienna by Professor Suess, comes to a different conclusion with regard to the origin of the gold, though confirming the correctness of Koch’s observations in every other respect. His reasons are not so clearly or definitely stated as those of Koch, but seem to be mainly the following:
1. The nature of the pebbles indicates that they came from quartz veins; they have the same colors as are described for the vein quartz of the Swasi-schists.
2. The form of the gold—in grains (Korner) and in flakes (Flittern)—as well as its distribution in the rock, indicates its. foreign origin.
3. As regards the critical question whether gold occurs in the
GEOLOGY OF THE SOUTH AFRICAN REPUBLIC Ig
pebbles, he says that after searching a great number of thin sec- tions he has found moss-gold in one or two; and moreover that after grinding up the rock and treating it with agua regia to dis- solve the free gold, the quartz fragments often showed included gold that had not been removed. He says, moreover, that Schmeisser answers this question in the affirmative.
This is not, however, a fair statement of the latter’s opinion, which in his own words is as follows: ‘The gold occurs almost entirely in the cement or matrix, in rare cases also in the pebbles. In the latter cases, however, it appears to be found only in the minute cracks that traverse the quartz.” Koch, from whose observations he formed his opinion, considers, as shown above, the gold in such cracks to be the secondary, as well as the quartz which encloses it. His (Schmeisser’s) final words with regard to whether the gold was deposited with the conglomerate as ‘fossil placer deposits,’ or was brought in subsequently in solu- tion, are: ‘The observed phenomena bear evidence in part for the one, in part for the other solution.”
Hatch, while declining to discuss the various hypotheses that have been brought forward, says, that the quartz pebbles are derived from veins in the Primary formation, but they are not the source of the gold because it does not occur in them (the pebbles); that the movements produced faulting ; that the dikes followed the fault fissures; and that the same planes acted as channels for the introduction of ascending mineralizing solu- tions. He says that no evidence has been found in favor of the locally prevalent theory that the dikes have acted beneficially, as regards gold contents, on reefs in their immediate neighbor- hood. :
The Future of the Rand.—So much attention has evidently been given to the question of the origin of the gold not only because of its intrinsic interest, but because it has an important bearing upon the future productiveness of the region.
The grounds on which auriferous conzlomerates outcrop have, it may be assumed, been all taken up or “pegged out,” as the South African phrase is; and already many so-called deep
20 S. f. EMMONS
level mines have been opened; 2. ¢., those whose surface lines do not include the outcrop, but which like the Tamarack and other conglomerate mines at Lake Superior, first reach the payable beds at considerable depths. How far from the outcrop toward the middle of the basin it may be profitable to open deep level mines, depends upon three factors:
1. The angle at which the beds descend, or the depth at which they will be found under a given point on the surface.
2. The vertical depth at which the difficulties of mining will neutralize the profit.
3. [he extent in depth, or the distance from the outcrop to which the conglomerate beds will continue to be payable.
If the gold is entirely placer gold, that is if it has all been brought into the beds mechanically, by the action of sea waves —there has been no suggestion of old river channels—it is evi- dent that there must be a limit to the distance from the shore to which so heavy a metal could have been transported.
That wave action may concentrate the gold in beach gravels sufficiently to constitute workable placers, has been proved on the coasts of California, Oregon and Alaska, though practically such placers have not yielded much profit to those working them, because the pay streaks are constantly shifted by storms and ocean currents.
The best authenticated instance of a fossil placer on an old shore line (not a river bed) known to the writer, is the conglom- erate at the base of the Potsdam sandstone, near Deadwood in the Black Hills. According to W. B. Devereux,’ who has given the best description of these deposits, the conglomerate which is rich enough to be profitably mined occupies a narrow belt, not over one and one-half miles wide, in the immediate vicinity of the Great Homeslates group of deposits in the underlying crystalline schists, from the degradation of which it is evidently derived. The gold inthe Potsdam quartzite of Bald Mountainand other dis- tricts of the Black Hills, however, is found, not in rounded pellets and flattened flakes, but finely divided and, when visible, is in the
tTrans. Amer. Inst. Mg. Engrs., Vol. XVII, p- 572.
GEOLOGY OF THE SOUTH AFRICAN REPUBLIC 21
brown powdery form that comes from precipitation. This he considers to have been chemically deposited as a result or sequence of the intrusion of igneous rocks in sheets or dikes, and more or less contemporaneously with the ores of silver that occur in these rocks.
That gold may be carried to a considerable distance from the shore inthe waters ofa sea or lake, is proved by deposits recently examined by the writer near Denver, Col., where payable placers occur, at fifteen miles or more from the ancient shore line of the lake, in Tertiary beds made up of detritus of granitic rocks that form the nucleus of.the Colorado range. In this case, however, the gravels that contain enough gold to be worked result from the rearrangement and concentration of the Tertiary lake beds in an ancient stream bed, the goldin the undisturbed Tertiary beds being too small in amount to-be of economic value.
Explorations within the conglomerate beds of the central dis- trict of the Rand have, as already shown, extended about one and one-half miles from the outcrop (which may be somewhere near the ancient shore line) and are still within the payable limit, but this does not prove that at several times that distance the payable limit may not have been passed. The fact, mentioned by Schmeisser, that the beds are generally richest at the bottom where the gravel is coarsest is, inso far, an evidence in favor of the placer theory. On the other hand many facts presented above seem incompatible with this theory, so that it would seem probable that while the beds contain gold that has been introduced mechani- cally, they also contain some that has been added chemically since the formation of the beds by concentration, either from adjoining sedimentary or from igneous bodies along areas that have been rendered accessible by dynamic movements.
As to the other two factors, it seems abundantly proved that the steep dips at the outcrop do not continue in depth, but at what depth the auriferous conglomerates will be found in the middle of the basin can only be finally determined by actual exploration with the drill.
The practical limits in depth at which mining can be profit-
BA S. &. EMMONS
‘ably carried on, have been recently extended by the experience of the Lake Superior mines, where the new shaft at the Calumet and Hecla mine is down below 4700 feet and destined to go to ‘5000. In this case, however, conditions are unusually favorable, for the increment of temperature with depth is, according toarecent statement of A. Agassiz,’ only 1° in 223 feet, or 79° at the bot- ‘tom of the present shaft. In South Africa the increment as deter- mined by Hamilton Smith is 1° in every 82 feet, which wouid produce a temperature of 100° at 3000 feet. This increment, ‘though below the average, is, there is reason to believe, somewhat -overestimated ; more recent estimates make it less than 1° for -every 100 feet, which would give only 108° (F) at 4000 feet.
Production, Past and Future —In conclusion it may be of inter- -est to consider some of the figures showing the gold production of ‘this remarkable region.
Its output for 1894 was gold to the value of 47,800,000 and ifor 1895 it is estimated to reach nearly 48,750,000. Hatch esti- mates that by 1900 the annual output will be over £20,000,000. ‘Up to July 1895 it had already produced £26,670,539. Esti- mates of the available supply of gold in the central district of ‘the Rand with its eleven and one-half miles of outcrop are given .as follows:
By Hamilton Smith - - - - - £325,000,000 “ Bergrath Schmeisser - - - - - 346,000,000 « F. H. Hatch - - - - - - 382,000,000
As these estimates have been arrived at independently and by somewhat different methods, Hatch allowing a greater depth for profitable working than the others, their slight difference is rather remarkable. Hatch further estimates a probable product for the whole region, including outlying districts, of 4£700,000,000, of \which £200,000,000 will be profit. This amount is greater than ithe product of the whole United States up to date.
S. F. Emmons.
‘t Am. Jour..Sci,, VoL L, Dec. 1895, p. 503.
IGNEOUS INTRUSIONS IN THE NEIGHBORHOOD OF tHe BUENCK HIS .;OE DAKOTA.
On the northern border of the Black Hills of Dakota, and situated partly in Wyoming, there are about a dozen hills of igneous rock, which not only add variety and beauty to the pic- turesque region where they occur, but are unique topographic features and furnish examples of a type of igneous intrusions that does not seem to have been clearly recognized.
The hills referred to, are known in the general order of their occurrence from east to west, as Bear Butte, Custer Peak, Terry Peak, Black Butte, Crow Peak in South Dakota, Inyan Kara, the Sun Dance hills, Warren Peaks, Mato Tepee or Bear Lodge, and the Little Missouri buttes in Wyoming.
Only a few of these hills have been examined by me, but such observations as I was able to make together with the des- criptions given by N. H. Winchellt and Henry Newton* of those not visited, show that they all have a common history and may be classed in a single group.
Each of these hills owes its existence to the injection from beneath of a column of molten rock into stratified beds, and the subsequent removal of the enclosing sedimentary strata so as to expose, with one exception, the inner core of plutonic rock. They differ from the laccolites described by G. K. Gilbert3, in the fact that the molten rock did not spread out horizontally among the stratified beds so as to form ‘‘stone cisterns,”
*Geological Report. In report of a reconnoissance of the Black Hills of Dakota made in the summer of 1874, by William Ludlow, Washington (Engineer Department, U.S. A.), 1875, 4to, pp. 21-66.
2Geology of the Black Hills (edited by G. K. Gilbert). In report on the geol- ogy and resources of the Black Hills of Dakota, by Henry Newton and Walter P. Jenney, Washington (Department of the Interior), 1890, 4to, 1-222.
3 Report on the Geology of the Henry Mountains; Washington (Department of the
Interior), 1877, 4to, pp. x.-160, Plates I.-V. 23
ears, Il, jour, Gio, WO, IOW., INO@. i
Fic. B.—Inner escarpment of limestone encircling the summit of Sun Dance Dome.
IGNEOUS INTRUSIONS IN THE BLACK HILLS 25
although some of the hills named, which had not been examined by the writer, may reveal this structure when more thoroughly examined. They differ, also, from volcanic necks like those of New Mexico described by Captain Dutton, to which some of them have a superficial resemblance, in the fact that the injected rock did not reach the surface so as to form either coulees or cinder cones. As they are composed of igneous matter forced into sedimentary strata and have a plug-like form, it will be con- venient to call them plutonic plugs.
In the hills examined by the writer the structure has been revealed in-varying degrees by denudation, so that an examina- tion of a few examples furnishes a series of illustrations ranging from an unbroken dome of stratified rock arching over the sum- mit of a concealed mass of plutonic rock, to imposing towers of columnar rhyolite several hundred feet in height, exposed by the removal of the softer strata into which they were intruded.
The first in this series is Little Sun Dance dome. This is a regular dome of stratified rock, about a mile in diameter, the outer layers of which have been removed and the inner ones of resistant limestone, deeply gashed by erosion, but not dissected sufficiently to expose the top of the igneous plug which presum- ably exists beneath.
The other extreme is shown by Mato Teepee. In this instance the arch of stratified rock which once surmounted the summit of the plutonic plug has been completely removed and the sur- rounding strata eroded away.
The rocks of which the plutonic plugs are composed have been studied microscopically by J. H. Caswell? and found to be rhyolite and sanadine-trachyte.
The rock composing the several hills is closely similar in general appearance and in chemical composition and crystalline structure. It is described in the report just referred to, as light-
*Mount Taylor and the Zuni Plateau. In 6th Annual Report of the U.S. Geo. logical Survey, 1884-5, Plates XI.—XXII.
* Microscopical Petrography of the Black Hills of Dakota. In report of the
geology and resources of the Black Hills of Dakota, by Henry Newton and Walter P. Jenney, Washington, pp, 489-527, Plates I.—-II.
le agra, JUL. JouRS GEO Vow. IN Nos
Fic. A.—Sun Dance Hill from the southwest.
Te e yy, a
ce
Fic. B.——Little Missouri Butte from the east.
IGNEOUS INTRUSIONS IN THE BLACK AILLS 27,
colored, compact and usually coarsely crystalline; and contains prominent crystals of sanadine, quartz, biotite and hornblende.
In the hills examined by the writer, namely, the Sun Dance hills, Mato Teepee and the Little Missouri buttes, the rock appeared to be of the same character in each instance. In hand specimens it was impossible to distinguish any essential differ- ence. For a more exact description of the rocks in question the reader is referred to Mr. Caswell’s report which contains the results of the only systematic study of them that has been made.
The stratified beds through which the plugs have been forced, vary in age from the Potsdam to the middle of the Cre- taceous. Ina conglomerate discovered by W. P. Jenney’ at the base of the Miocene in the neighborhood of the Black Hills, pebbles of igneous rock were found which must have been derived from the hills now claiming our attention. The date at which the plugs were formed is therefore somewhere between the Middle Cretaceous (Fort Pierre group), which was disturbed and altered by their intrusions; and the base of the Miocene, at which date they were exposed to erosion and contributed pebbles to neighboring streams.
In discussing the date of the origin of these rocks, Newton? observes that the interval mentioned above, witnessed the depo- sition of the Niobrara, Fort Pierre, Fox Hill, Judith River and Fort Union terrains, which represent a total depth, in the upper Missouri region, of about 4000 feet of sedimentation. The date of the igneous activity is therefore very far from being definitely established, and its relation to the main Black Hills uplift is not determined. The igneous rocks may have been in place and even ancient when the elevation of the Black Hills began, or they may have been forced up while the greater movement was in progress.
With this introduction, such facts of geographical and geo- logical interest as are available concerning these remarkable intrusions will be presented.
* Geology of the Black Hills, p. 220.
G20 220t
PAs IWUL, Joo, GOL. WO. IW, INO. i
Fic. B.._Mato Teepee from the southwest.
IGNEOUS INTRUSIONS IN THE BEACK HILLS 29
Little Sun Dance dome.—This hill, sometimes called Green Mountain, is situated about two miles northeast of the town of Sun Dance, the county seat of Custer county, Wyoming, and about three miles north of a larger uplift of the same character, known as Sun Dance hill.
A view of Little Sun Dance as seen from the topographic monument on the summit of its more imposing companion, is given in Fig. A, Plate I. This dome is remarkably regular from whatever direction it is seen, and is composed of stratified rocks which have without question been elevated by a force acting from below directly upward. The summit of the hill consists of Carboniferous limestone, the crown being an unbroken dome. About this inner dome and dipping sharply in all directions are strata of purplish limestone belonging to the Red Beds or Tri- assic system. This resistant layer has a thickness of about twenty feet,and was once continuous over the top of the dome, but has been removed from the summit by erosion, and several radiating gorges cut by streams in the portion of the envelope which remains.) Between the drainage lines the strata extend far up on the sides of the dome so that the edge of the outcrop when followed about the hill forms a zigzag line. As described by Newton, the exposed edge of this limestone resembles the broken edge of a piece of paper that has been punctured by a sharp pencil. Although the strata have been bulged upward, they have not been shattered, the apparent radial breaks being due entirely to erosion. Resting on the limestone, are soft, easily eroded shales, a hundred feet or more in thickness. The position of this bed is indicated about the base of the hill by a smooth, grassy valley a few hundred feet in breadth. On the outer side of this valley is a rampart, more or less well defined, of sand- stone layers, which dip away from the dome in all directions but present a steep inner escarpment. The sandstone and shale belong, together with the purple limestone, to the Red Bed sys- tem, and are the highest or youngest strata exposed in the immediate vicinity.
The streams which have eroded deep trenches in the sides of
30 USIRAIGIL, Cy LLOSSIGILIL
the dome, radiate from its center and, with one exception, are active only during wet weather. At the head of a deep, wooded gorge which leads northward from near the center of the uplift, there is a small spring from which flows a perennial rivulet. A view looking down this channel is shown in Fig. B, Plate I. The rock forming the cliffs is purple limestone and shows the char- acter of the zigzag escarpment that Newton compares with the torn edges of the paper through which a pencil has been forced.
An examination of the bottoms of the drainage channels on the summit and sides of the Little Sun Dance dome, and of the débris with which they are partially filled, failed to reveal even a fragment of igneous rock.*
The most interesting facts connected with the geology of the Little Sun Dance dome are, that the rocks were elevated by an extremely local force acting from below upward, and that the strata which suffered deformation were not fractured, or sensibly metamorphosed, during the process. The absence of fractures in the crown of the dome, as well as the vast amount of erosion which is known to have taken place in the region in which it is situated, show that the bending of the rocks must have taken place under a great weight of superincumbent strata.
Sun Dance lill—vVhis hill is not only higher and larger than the one just described, but differs from it widely in its topo- graphic form. As seen from Little Sun Dance, it represents a bold scarp to the west and declines more gently and with many undulations in other directions. The western scarp (Fig. A, Plate {I) is composed of plutonic rock and has steep talus slopes at its base. The flanks of the hill, especially on the east, are com- posed of Red Beds, somewhat upturned. These strata extend entirely about the central core of intruded rock and slope away from it at low angles in all directions.
A geologist on visiting Sun Dance hill, after examining its smaller neighbor, would say at once that the two uplifts are very similar in many ways. In Sun Dance hill the intruded rock was
*This hill is marked as igneous on the map accompanying Newton’s report on the geology of the Black Hills.
IGNEOGS INTROSIONS TN THE BLACK HILLS 31
forced to a higher level than the present crown of the Little Sun Dance dome, and has been well exposed by the removal of sur- rounding strata. As these hills stand near together on the same plain, it is evident that they have been exposed to the same erosive agencies. The larger hill is higher for the reason that the plug forming its center was forced to a higher level in the stratified beds and is also of greater diameter than the similar plug which presumably caused the upheaval of the smaller hill. It is also to be noted that the sedimentary beds surrounding the larger intrusion show less disturbance than those around the smaller uplift, which has been dissected less deeply in reference to the top of the column of igneous rock. This indicates that the greatest amount of disturbance among the stratified beds occurred near the summits of the intruded columns.
Mato Teepee—This remarkable tower has been described — very fully by Newton," and to his account of it we are indebted for the measurements here used. It stands on the west bank of the Belle Fourche River, about twenty-two miles northwest of the Sun Dance hills, and six miles southeast of the Little Mis- souri buttes, next to be described.
As stated by Newton, the name “Bear Lodge” is used on the earliest maps of the region, although more recently it is said to be known among Indians as ‘‘the bad god tower,” or in better English, “the Devil’s tower.” Mato Teepee, meaning Bear lodge, seems to have been the original Indian name and will be used in this paper.
Something of the impressive grandeur of this lonely column may be gathered from the accompanying pictures. Fig. A, Plate III., is reproduced from a photograph taken on the banks of the Belle Fourche about two miles in a direct line south of the tower. Even at this distance the clustering columns that com- bine to form the structure may be easily distinguished. Another view, showing the columnar structure still more clearly is also given on Plate III., which is from a photograph taken about a quarter of a mile southwest of the tower.
*Geology of the Black Hills, pp. 200-202, and frontispiece.
B82 USUGHIBIL (Cy LO SSIBIESL
The platform surrounding the base of Mato Teepee as seen in Fig. A, Plate III., is not a remnant of a coulee of lava or the remains of an ancient cinder cone, as might be supposed from a distant view, but is composed of sandstones and shales belong- ing to the Red Beds and the Jurassic formations. The stratifi- cation of these beds, even up to the base of the tower, is hori- zontal and undisturbed. Some change in texture, however, may be observed in the strata in the immediate vicinity of the intruded rocks, showing that they were hardened and somewhat metamorphosed when the igneous material was forced in among them.
When Mato Teepee is seen from almost any locality in the valley of the Belle Fourche within a radius of several miles, one is not only forcibly impressed by the grandeur of the monu- mental form that dominates the landscape, but is delighted by the brilliant and varied colors of the rocks forming the sides of the valley and the immediate base of the tower. The Red Beds in the lower portion of the river bluffs show many variations of pink and Indian red, and have been sculptured into architectural forms of great beauty. The less brilliant Jurassic sandstones resting upon them and forming the upper portions of the bluffs, serve to carry the eye from the rich colors below to the dark forest of pines that grow above and to the still more somber precipices of the great tower which always appears in bold relief against the sky.
The platform on which Mato Teepee stands is 500 feet above the river, while the tower proper rises almost vertically 626 feet above it. The tower is nearly rectangular in cross section; the width at the summit from north to south, being 376 feet, and the width at the base 796 -feet.t The shaft of the column is com- posed of clustered prisms which extend from base to summit without cross divisions. These prisms are usually pentagonal, although other forms are not uncommon. Most frequently they have a diameter of from eight to ten feet. Each prism tapers somewhat toward the top, and near its upper extremity is cracked
t Geology of the Black Hills, p. 201.
IGNEOUS INTRUSIONS IN THE BLACK HILLS 33
and discolored by weathering. At the base of the tower the columns in most instances, except at the southeast corner, curve abruptly outward, and, at the same time, increase somewhat in size. On the west side they become nearly horizontal and are soon lost to sight beneath accumulations of débris. Near the base of the tower, just above the treetops, as seen in Fig. B, Plate III., the rock loses its columnar structure, becomes massive and breaks with an irregular fracture. On the sides of the tower there are a few places where the lower portions of individual prisms have fallen away, leaving the upper two or three hundred feet still in place. In such instances one has a good view of a section of the prisms, which are seen to be four, five or six-sided.
Owing to the abrupt outward curvature of the columns at the west base of the tower, the fragments that have fallen from above have been thrown farthest out on that side and now form an extremely rugged talus in which fragments of huge columns lie piled in endless confusion one on another, suggesting the ruins of some mighty temple.
As shown in the accompanying illustrations, the sides of the tower are nearly perpendicular. This fact is still more impres- sive in nature, especially when one stands at the base of the great prisms, each of which is an uniform column over 500 feet high, and looks upward. The strongest and most experienced mountain climber must pause when he has scaled the rugged cliffs which form the immediate base of the tower and gains the point where the individual prisms make their abrupt curve and ascend perpendicularly. Beyond that point no man has ever reached, and, it is safe to say, never will, unaided by appliances to assist him in climbing.
To gain a comprehensive view of Mato Teepee and of its relations to neighboring cliffs and plateaus, one should go about two miles west from the tower and ascend to the top of the table- land which has been cut away to form the valley of the Belle Fourche. Standing on the border of this table-land which rises more than 1000 feet above the silvery thread marking the course of the river in the valley below, one is a little lower than the
34 USIRAUIBIE (C, SOS SIBILIL
top of the tower which is the most prominent object in the land- scape. On looking west from this point of view, it is at once apparent that the observer is on the immediate border of a table- land which stretches away far beyond the limits of view. On this plateau and four or five miles distant, stands a group of three hills known as the Little Missouri buttes.
It requires but a glance from almost any commanding posi- tion in the neighborhood of Mato Teepee, to show that the valley of the Belle Fourche has been eroded in the flanks of a broad uplift, which culminates several miles to the east in a great dome-shaped elevation known as Mount Warren. In fact the rocks removed to form the valley hardly interrupt the gentle sweep of the sky-line as one follows the profile of the land on looking southwest. It is at once apparent to every observant person who looks down on the valley of the Belle Fourche from a commanding station, that the stratified rocks which form the bordering bluffs of the valley were once continuous, and that the whole depression has been formed by erosion. Mato Teepee rises from the bottom of this valley and must at one time have been surrounded by the strata that have been carried away. It is a monument of erosion not unworthy of the great events it commemorates. Restore the rocks which have been removed in order to form the valley up to the level of the cliffs on which the reader is supposed to stand, and Mato Teepee would be nearly buried. A thousand feet of rock have been removed to form the valley about it, but this does not represent the entire amount of the erosion that has taken place. This is shown by the his- tory of the Little Missouri buttes which stand on the plateau stretching west from Mato Teepee. These hills are of the same nature as the great tower in the valley below, and were intruded among sedimentary strata that rested on the platform above which they now rise. As their tops are more than 500 feet above the plateau, it is evident that more than this thickness of rock has been removed in order to expose them.
As erosion goes on, the rocks forming Mato Teepee will crumble and be carried away by the stream which is even now
IGNEOUS INTRUSIONS IN THE BLACK HILLS 35
encroaching upon its base, while the plugs forming the Little Missouri buttes will become more and more prominent as the stratified rocks are removed from about them, and when the valley of the Belle Fourche shall have been broadened so that the waters of the river wash their bases, will form towers of the Mato Teepee type.
The total amount of erosion that has taken place in the region about Mato Teepee cannot be accurately determined from the study of the local topography, but is certainly greater than the vertical distance from the bottom of the valley to the top- most crag of the Little Missouri buttes, that is, over 1500 feet. As shown by Newton, more than 4000 feet of Cretaceous and Tertiary strata have been removed from the Black Hills region.
The Little Missouri Buttes—These buttes, as already stated, are formed of igneous rocks of the same character as those com- posing the Sun Dance hills and Mato Teepee. They are three in number and occupy the angles of a triangle, the distance between them being about three-fourths of a mile. Among the Indians they are said to be designated by a term which means “the buttes that look at each other.”’
The summits of the Little Missouri buttes are of bare rock, sometimes showing a columnar structure, and resemble the summit of Mato Teepee, except that they are less flat. The junction of the igneous rock with the surrounding Cretaceous sandstone is obscure, but the stratified rocks are well exposed near at hand and gives no indication of having been disturbed in bedding or altered in texture. Newton’ reports that in one or two localities near the base of the buttes a tuff-like rhyolitic breccia was found in which were imbedded fragments of both sandstone and rhyolite. ;
The view of the buttes here presented, Plate II. (in which only two of them are seen, the third being to the left and beyond the field of view) is from a photograph taken at a locality on the Cretaceous plateau about a mile distant from the nearest hill in the direction of Mato Teepee.
* Geology of the Black Hills, p. 203.:
36 ISRAEL ©. RUSSELL
The Cretaceous sandstone surrounding the base of these ‘buttes is the youngest of the stratified rocks which come in immediate contact with the igneous intrusions we are studying, and presuming that all the igneous rocks are of the same date, records the upper limit as nearly as can be determined, to be placed on estimates of the time of their origin. That is, they are younger than the Middle Cretaceous.
Inyan Kara.—This lone butte stands in Wyoming on the west side of the main uplift of the Black Hills. It has not been seen by the present writer except from a distance but has been described by both Winchell and Newton. As Newton’s visit was the more recent we quote his description almost entire :*
Its name first appeared on a map published by Lieut. Warren in 1858, and as translated for him, signifies ‘‘the peak which makes stone.” Its summit is 6600 feet above the sea, and has an elevation of 1300 feet above the bed of the Inyan Kara Creek near by. The igneous mass of the peak occupies the center of what in form resembles a crater, for separated from it by an annular valley there is an encircling ridge or rim whose top is 500 feet below the summit of the peak. This rim is formed of Red Bed limestone rising up from under the surrounding red clays at an angle of about 40° and completely encircling the peak except at a narrow break on the northeast side where the drainage escapes. The limestone wraps around the outer slope of the peak like a cloak, conforming to all local changes of dip and is without fracture. The upper red clays of the Red Beds lay up against this limestone, and in conformity with it dip away in all directions. On the inside of the rim is the annular valley, surrounding the igneous nucleus and having a width, from rim to center of peak, of from one-half to three-fourths of a mile. It has evidently been formed by the denudation of the easily eroded strata beneath the limestone.
From the midst of the crater-like depression the peak rises so abruptly that there is but one side with an easy slope for climbing. The summit is a broad but very irregular area, whose
* Geology of the Black Hills, pp. 197-199.
IGINE OTS INTROSIONS JN THE BLACK HILLS Bi
larger dimension has a bearing of about 30° West of North and upon which the rock is well exposed. It is a hard, highly feld- spathic trachyte, and on weathered surfaces large and well formed crystals of feldspar were seen in great abundance, giv- ing the weathered mass a porphyritic appearance. Its mass. is notably magnetic. The rock shows well marked cleavage or jointing planes, nearly vertical, in two series. The first runs. toward the northwest and the second towards the west, divid- ing the rock into prisms and producing a quasi-columnar structure.
Though on such a large scale, the entire upheaval being prob- ably two or three miles in diameter, the peak has essentially the structure of the Sun Dance hills. Among the uplifted beds sur- rounding Inyan Kara no strata were recognized excepting Red Bed limestone and the underlying, impure, reddish sandstone, and beyond the immediate base of the outer slope no disturbance was indicated. Indeed, the red arenaceous clay is too nearly structureless to retain readily such evidence.
The high angle at which the stratified rocks surrounding the base of Inyan Kara dip away in all directions from the central core, shows that there was more disturbance caused by this. intrusion than in any of the similar examples previously described in this paper. The igneous rock was also forced to a higher level than in the Sun Dance hills, and was greater in mass than in any of the similar hills in the neighboring part of Wyoming, with the exception of Mount Warren.
Complete as is the exposure of the igneous rock in Inyan Kara, it is to be remarked that no expansion of the central plug so as to form a coulee or a laccolite, is mentioned by the geolo- gists who have examined and described it.
Bear Butte—On the northeast side of the Black Hills and about six miles east of the town of Whitewood, there is another conspicuous butte, similar in many ways to Inyan Kara. This hill, known as Bear Butte, rises from Middle Cretaceous shales but is surrounded at its immediate base by older rocks which dip away in all directions. It has been described by F. V-
38 USIRAUBIE Cn IAI SSIBIE,
Hayden,’ N. H. Winchell? and Henry Newton,3 and from these descriptions the following has been compiled.
The butte rises 1200 feet above the surrounding plain and attains an elevation above the sea of 4570 feet. As seen from the north, it is a simple cone, but from the east and west summit appears as a ridge several hundred feet in length, with a trend about North 40° West. The strata which are exposed about its base and dip away from it in all directions, are composed of rocks of all ages from the Middle Cretaceous to the Potsdam, inclusive. A dense quartzite, probably of Potsdam age, occurs at the immediate base of the butte in vertical strata, but does not form a continuous circular outcrop.
The rock of which the butte proper is composed is very sim- ilar if not identical with that forming Inyan Kara, Bear Lodge, etc. It is crossed by cleavage plains but is not columnar. When freshly broken it is gray in color but when weathered it appears nearly black. The débris in the immediate vicinity of the butte is so abundant that good exposure of the stratified rocks sur- rounding its base are seldom seen. The harder beds in these strata, however, influence the relief sufficiently to show the presence of an encircling rampart of the same character as the much more conspicuous one, about the base of Inyan Kara. Denudation has stripped the central plug of igneous rock of its enveloping stratified beds almost as completely as in the case of the great tower in the valley of the Belle Fourche.
Crow Peak.—This peak is situated in the northern part of the Black Hills, about five miles west of the town of Spearfish, and rises to an elevation of approximately 1,500 feet above bottom of the Red Valley, which skirts its northern base.
It is described by Newton,‘ as a pustular outbreak of igne- ous rock through Red Bed limestone. As seén from the west it appears as two peaks closely united; the southern one is the
* Trans. Amer. Philo. Soc., Vol. XII., n. s., 1863, p. 28. ? Reconnoissance in the Black Hills, pp. 55-56.
3 Geology of the Black Hills, pp. 195-197.
4 Geology of the Black Hills, pp. 194-195.
IGNEOUS INTRUSIONS IN THE BLACK HILLS 39
rhyolite core, while the northern one is a portion of a rampart of sedimentary beds which once entirely surrounded it. This hill, like the others in the series to which it belongs, owes its exist- ence, if the present writer’s views are correct, to the intrusion of a plug of igneous rock vertically upward through nearly hori- zontal sedimentary beds and the subsequent exposure of the intrusive rock by erosion. Terry and Custer Peaks. marks in the northern portion of the Black Hills. They have been described by Newton," as pustular outbreaks of igneous matter and belong to the series of intrusions to which attention is here directed, but so far as one can judge from the published descriptions, they offer no important features not already
These are other prominent land-
noticed in this paper.
Warren Peak.—This is the largest and in fact the only truly mountainous mass of igneous rock on the outskirts of the Black Hills, and may differ materially in the mode of its formation from the plugs of crystalline rock we have already noticed. Its broad extent and the manner in which the surrounding stratified rocks dip away from it in all directions, seems to indicate that it is a true laccolite, very similar to those of the Henry Mountains. The description given below is copied from Newton.’
Warren peaks are the crowning points of the “ Bear Lodge Range,” an elevated, broken plateau between the Redwater valley and the Belle Fourche. The peaks are not remarkably prominent, but their total elevation above the sea, 6830 feet, is equal to that of some of the principal peaks in the central por- tion of the Black Hills, while their height above the Red Valley immediately south, is about 1800 feet. The trachytic area to which they belong is the largest of the whole group, and covers fifteen or twenty square miles. Around this the strata of the sedimentary series are uplifted and arranged in concentric circling outcrops, so as to make a sort of miniature copy of the hills. The trachytic nucleus has an extension from northeast to
* Geology of the Black Hills, pp. 192-194. ? Geology of the Black Hills, pp. 199-200.
40 USAGI, (Cy die GS SIEILIL
southwest of about eight miles, and a width of two or three miles. Its surface consists of high, rounded, grass-covered hills, with little or no timber, and from this rise the two or three more elevated points to which the name Warren peaks has been applied. These more central points are surrounded by smaller and less prominent peaks, which are separated by deep ravines or gulches forming the lines of drainage. Besides this great nucleal mass of igneous rock, several outbursts, very local in character, were observed in the zone of encircling strata. The rock is a trachyte, dark gray in color, and containing frequently large and perfect crystals of sanadine which give it a porphy- ritic character. Small crystals of mica and hornblende are also prominent, and the rock yields more to weathering than that of some of the other peaks. In different portions of the district the rock varies somewhat in its character, though evidently of the same general nature.
The encircling zones of sedimentary rocks include the Pots- dam below and the Jura above. Their dip is quaquaversal and is usually quite regular, the angle varying from 20 to 30 degrees.
The Potsdam sandstone which immediately overlaps the base of the igneous mass has been greatly metamorphosed. When the rock was shaly it has been changed into a hard fissile slate, scarcely recognizable as of sedimentary origin; and the pure sandstone strata have been converted into compact quartzite often of a very white color. In several places the igneous matter seems to have penetrated between the strata, which are scarcely distinguishable from the injected rock, and in many cases the metamorphosis appears to have been performed by the action of heated waters, for the sandstone was found penetrated irregularly by well-formed crystals of feldspar. On the west side, near the middle of the formation were found layers of argillaceous sand- stone covered by large branching fucoids peculiar to the Potsdam, and some of the upper layers of the sandstone are perfectly riddled with Scolithus holes. The Potsdam, Carboniferous and Red Beds are well exposed in many of the canyons which radiate from the central area carrying the drainage eastward to the Red-
IGNEOUS INTRUSIONS IN THE BLACK HILLS 41
water, or westward to the Belle Fourche. On the south and east, facing Sun Dance hills, the Red Bed limestone forms the outer slopes, dipping under the red clay of the Redwater Valley, On the north and west, however, the Jura is well exposed and capping this the Dakota sandstone.
Though on a grander scale and exposing a larger area of igneous rock than the other neighboring centers of intrusion, the Warren peaks show the same character of pustular eruption.
In a recent paper on the geology of the Black Hills, W. O. Crosby,’ has devoted a few pages to the consideration of the igneous intrusion described in this paper, in which it is claimed that they are true laccolites. He also presents reasons for con-
b
cluding that the hypothesis of ‘‘ Pustular Eruptions,” advanced by Newton is not warranted by the facts.
As I am unfamiliar from close inspection with the larger igneous masses of which Warren, Terry and Custer peaks are lead- ing examples, I am unable to offer an opinion as to whether they are laccolites or not. Their great size and the manner in which the surrounding sedimentary beds have been disturbed and altered in their vicinity, certainly seem to indicate that such was their mode of origin. In the case of the Sun Dance hills, Mato Teepee and the Little Missouri buttes, however, which I have examined and also in the case of Inyan Kara and Bear Butte, which I have seen from a distance, and of which detailed descrip- tions have been published, the evidence does not sustain the assumption that they are laccolites.
The absence of volcanic débris except in the immediate vicin- ity of these hills, indicates that the intruded rock did not spread widely among the stratified beds or overflow the surface. This, as well as the fact that in a series of examples ranging through all degrees of erosion from the unbroken dome of Little Sun Dance hill to Mato Teepee with its majestic tower over 600 feet high, and Bear butte, 1200 feet high, neither of which exhibit evidence of laccolitic expansion, seems sufficient to prove
** Geology of the Black Hills of Dakota.” Boston Soc. Nat. Hist., Proc., Vol. XXIII. pp. 488-517.
42 USIKAIBIE (Cn IRS SVBIEIC
that they cannot be referred to the class of intrusions that has its type in the Henry Mountains.
What precise mode of origin Newton had in mind when he compared these intrusions to bubbles ina viscid lava mass, is not clear. As the nature of laccolites was not understood at the time of his exploration, a comparison with that form of intrusion could not be made.
That the magma composing the hills described in this paper was cooled slowly at a considerable distance below the surface, and consequently under great pressure, is indicated by their geo- logical associations and is proven also by the character of their crystalline structure. They are coarse grained or porphyritic, instead of being glassy and imperfectly crystallized. In no instance has the rock assumed the form of obsidian, pitchstone, pearlite, etc., or been expanded into scoria and pumice, as one would expect had the magma cooled at the surface.
None of the plutonic plugs examined by me are associated with dikes or faults. In fact dikes appear to be wanting in the Black Hills region, since they do not seem to be mentioned by any of the geologists who have written concerning it. It is reasonable to suppose that the magma which rose from below and formed the plug-lhke intrusions described above, found its way through fissures in the lower series of stratified rock, but proof that this was the case is wanting. How the stratified beds below the domes that covered the plugs were displaced, or per- haps fused, so as to furnish room for the passage of the intruded material, is not clear.
A comparison of the structure of the Sun Dance hills, Inyan Kara, etc., which are from one to two or three miles in diameter, with the structure of the dome that once covered Warren Peak, and had a diameter in one direction of two to three miles, in another direction of about eight miles and a height of two or three thousand feet; and still again with the structure of the vastly greater dome from which the Black Hills, as we know them, were sculptured, brings out striking similarities. Had no erosion taken place since the Black Hills uplift began, as is shown
IGNEOUS INTRUSIONS IN THE BLACK HILLS 43
in a contour map by Newton and Gilbert,’ it would now form a great, elongated dome, about 80 by 160 miles in diameter, and rising 7000 feet above the encircling plain. The central core of this vast dome is composed of schist and granite, from which the surrounding sedimentary beds dip away in all directions in the same manner as they do about the Sun Dance hills.
Great as is the Black Hills dome, it is far surpassed in size by a similar uplift forming the Big Horn Mountains, rising some 180 miles to the westward, and by several of the ranges in the Park Mountains, Colorado.
Some of the thoughts suggested by these and other compari- sons, with reference to the origin of great domes in a broad region of horizontal rocks, will be presented in a future paper in this JOURNAL.
ISRABL IC. KUSSELL:
t Geology of the Black Hills, Pl. cf p. 208.
Was, GIZOILOGY Ole INGEN ISLAIMIPSISUURIE..
CONTE NGS: The First Geological Survey.
The Second Geological Survey.
Peculiarities of this Survey.
Topographic Results.
Connection with Work in Adjoining Territory. Determination of the Order of the Groups of Schists. Correlation with Recognized Standards.
Surface Geology.
Tue first public notice of the importance of examining the mineral resources of New Hampshire is contained in a message of Governor Levi Woodbury to the legislature in 1823. He recommended the institution of an agricultural survey with a view to chemical analyses of the various kinds of soils. Had this recommendation been adopted, New Hampshire would have been the first of the United States to inaugurate a scientific survey of her mineral resources.
The Furst Geological Survey.—In 1839, after earlier sugges- tions from the executive, the legislature passed an act to pro- vide for the geological and mineralogical survey of the state, appropriating for the purpose the sum of two thousand dollars annually for three years. Dr.C.T. Jackson, of Boston, received the appointment of geologist, and with several assistants con- ducted the work of the survey, and published the following reports:
First Annual Report on the Geology of the State of New Hampshire, 8vo, 164 pp., 1841.
Second Annual Report on the Geology of the State of New Hampshire, 8vo, 8 pp., 1842.
Final Report on the Geology and Mineralogy of the State of New Hamp- shire, with contributions toward the improvement of Agriculture and Metal- lurgy, 4to, 378 pp., 11 plates, 1844.
Views and Map of the Final Report, reprinted, 4to, 20 pp., 8 plates, 1845.
44
GEOLOGY OF NEW HAMPSHIRE 45
The character of this final report may be summarized as follows: 44 per cent. of the pages is occupied with a description of the method of procedure and notes upon the geological and mineralogical results in the form of an itinerary; 20 per cent. relates to economic geology; 22 per cent. to agricultural geol- ogy and chemistry, and the remaining 16 per cent. is devoted to such miscellaneous topics as barometrical tables, the official documents relating to the survey, glossary and index. One of the assistants, was Professor J. D. Whitney, of Cambridge; Dr. E. E. Hale, of Boston, aided in the exploration of the White Mountains.
The method of exploration or reconnaissance adopted by Dr. Jackson was based partly upon the structure. Knowing that the strata pursue a general northeast course, it was proposed to cross them several times at right angles to their outcrops, and also along the lines of strike. These lines divided the territory into triangular areas whose outside boundaries became known, and the various excursions for study were planned across several tracts, depending somewhat upon roads and settlements. Four cross sections are described and figured, viz., from Portsmouth through Concord to Claremont; from Concord to Wakefield ; from Concord to Winchester; from Winchester to Haverhill. There is also a longitudinal section along the Connecticut River from the Massachusetts line to Haverhill; and from Haverhill to the extreme northern part of the state. Six dis- tinctions are made: (1) Granite, syenite and gneiss; (2) mica slate; (3) hornblende rock; (4) argillaceous slate; (5) drift; (6) alluvium. Symbols indicate the location of twenty kinds of ores and minerals, quarries,. dips of strata and anticlines.
The nature of the work was mineralogical. Scarcely any assistance was acquired from these reports for the later geolog- ical studies. The general view of age and structure presented was that of the older authors, all granite being regarded as “Primary,” and the dips of the strata outward in every direc- tion from an igneous center. This conclusion is best shown in an ideal section across northern New England. At the White
46 Cte, tall ICL CO OCIS
Mountains granite prevails, having mica slate and gneiss dip- ping to the east in Maine; similar rocks occur on the west side, together with ‘‘Cambrian,” all inclined towards: Lake Cham- plain. The Green Mountains are made out to be an immense mass of quartz rock. There seems to be an important element of truth in this representation, while the details cannot be relied upon. In the neighborhood of the White Mountains the older rocks make their appearance, but granite does not constitute the central axis of the White Mountains; the strata are not uniformly regular in their dips outward from the axis, and the Green Mountains are not made of quartzite.
It is difficult to find accurate reports of the cost of Jack- son’s survey, but it would appear probable that the explorations and studies cost less than $10,000, and the expense of publica- tion was met by other appropriations. Owing to the wish to reduce the size of the last item of expenditure, the map has no coloration, so that it is difficult to pronounce upon its value.
The Second Geological Survey.—in 1868 the legislature passed an act providing anew for the geological and mineralogical sur- vey of the state, for which the sum of $3500 was annually appropriated. It was stipulated that brief annual reports show- ing the progress of the survey should be made, and ‘when the survey shall be completed, a report of the same, accompanied by such maps and drawings as may be necessary to elucidate and exemplify the same, shall be published under the direction of said state geologist.”
On the eighth of September 1868 the writer was appointed state geologist by Governor Walter Harriman. The work was prosecuted for ten fiscal years, the. time used for exploration being somewhat less than would appear from the records. So far as the survey had a connection with the state government, its enabling act carried two favorable provisions: (1) It was not necessary to go before the legislature every year with a request for a new appropriation. If this had been the case, probably the life of the survey would not have extended beyond three years. (2) Only brief reports of progress were expected annually.
GEOLOGY OF NEW HAMPSHIRE 47
I have taken great pains to determine exactly the cost of every part of this survey to the state, including the explorations, printing the annual and final reports, but not the cost of distri-
bution. Expenses of exploration and study, - - $32,199.27 Annual reports (1500 copies), - . - 1,459.80 Final report (1000 copies), - - - - 33,959.17 Relief map and cases for museum, - - 500.00
$68,118.24
The following titles express the official reports to the state:
First Annual Report upon the Geology and Mineralogy of the State of New Hampshire, by C. H. Hitchcock, state geologist, 12mo, 36 pp., I map.
Second Annual Report upon the Geology and Mineralogy of the State of New Hampshire, by C. H. Hitchcock, state geologist, 8vo, 37 pp., 1 map.
Report of the Geological Survey of the State of New Hampshire, show- ing its progress during the year 1870, by C. H. Hitchcock, state geologist, 8vo, 82 pp.
Report of the Geological Survey of the State of New Hampshire, show- ing its progress during the year 1871, by C. H. Hitchcock, state geologist, 8vo, 56 pp., I map.
Report of the Geological Survey of the State of New Hampshire, show- ing its progress during the year 1872, by C. H. Hitchcock, state geologist, 8vo, I5 pp., I map.
The Geology of New Hampshire. A report comprising the results of explorations ordered by the legislature, by C. H. Hitchcock, state ‘geologist, J. H. Huntington, principal assistant. Part I. Physical Geography, Royal 8vo, 680 pp., 49 plates, 1874.
The Geology of New Hampshire, etc., by C. H. Hitchcock, state geol- ogist, J. H. Huntington, Warren Upham, G. W. Hawes, assistants. Part II., Stratigraphical Geology, Royal 8vo, 696 pp., 40 plates, 1877.
The Geology of New Hampshire, etc., by C. H. Hitchcock, state geologist, J. H. Huntington, Warren Upham, G. W. Hawes, assistants. Part III., Sur- face Geology. Part IV., Mineralogy and Lithology. Part V., Economic Geology. Royal 8vo, 760 pp., 30 plates, 1878.
Atlas accompanying the report on the Geology of New Hampshire, by C, H. Hitchcock, state geologist, 1878. Folio containing seventeen maps and profiles.
Peculiarities of this survey—Geological surveys may be classi- fied in groups. Those prosecuted in the same decade will be
48 C. H. HITCHCOCK
found to be very much alike. The surveys more or less coeval with that of New Hampshire, 1868 to 1878, were the following: Canada, where the directorship was transferred from Sir W. E. Logan to A. R. C. Selwyn in 1870; the geographical and geo- logical work in the territories under F. V. Hayden extending from 1867 to 1878; the fortieth parallel survey under Clarence King, 1867 to 1880; the Wisconsin survey, T. C. Chamberlin, 1873 to 1879; the Michigan survey, 1869 to 1876, under Rominger, Brooks and Pumpelly, and the Ohio survey under Newberry, 1869 to 1878. The second geological survey of Pennsylvania began in 1874, and that of Minnesota in 1872. It was an honor to any geologist to have been a contemporary worker with the gentlemen who directed these several surveys. But the style of work in vogue then should not be expected to equal that which is being executed in the nineties, with the multitudinous facilities of the later period.
The new methods of petrographic study were first exempli- fied in these surveys by the report of Ferdinand Zirkel upon Microscopical Petrography for the Fortieth Parallel organization in 1876, and by Dr. G. W. Hawes upon the Mineralogy and Lithology of New Hampshire in 1878. Both of these treatises were models in their way, and were carefully studied by workers in this field for many years. Mineralogists not connected with surveys engaged in corresponding studies even earlier. Dr. Hawes continued his investigations into some of the New Hamp- shire rocks after the publication of his report, as is evidenced by his descriptions of the contact phenomena between the Albany granite and mica schist upon Mount Willard, and upon the dis- similar dikes found at Campton. His early death cut short a most promising career. .
The progress of the New Hampshire survey was much retarded by the presence of a dense forest covering an area of 2000 square miles in the northern portion of the state, and by the difficulties of transportation. All this mountainous forest had to be trav- ersed on foot mostly without paths or guides. From the summit of Mount Washington a sea of mountains is visible. Every one
GEOLOGY OF NEW HAMPSHIRE 49
of them was visited by some member of the survey, observations made and specimens preserved for study. At the present time railroads thread three-fourths of this forest country, and by exca- vations and the removal of the forests, facilities for exploration have been greatly increased. Had the survey of this region commenced fifteen years later, the information acquired could have been gathered in a fourth part of the time actually taken.
Connection with work in adjoining territory.— The geology of New Hampshire is intimately connected with that of Vermont and Canada. The writer had fortunately been connected with the survey of the former as principal assistant, and was familiar with what had been published for both adjoining districts, and had taken pains to revisit typical and extra-limital areas during the progress of the explorations. The published New Hamp- shire map covers fully a third part of eastern Vermont and an important section of Canada, for which information was based upon a manuscript left by Sir W. E. Logan, interpreted in the light of later studies. The chief support of our stratigraphical conclusions lay in the anticlinal structure of the Green Moun- tains. My advisers, Professor James Hall, Sir W. E. Logan, and Professor J. D. Dana, taught me that this structure was synclinal. After measuring thirteen general sections across this range, it became clear that my guides were in error. Their great anxiety to maintain the synclinal notion had been exerted in order to sustain the doctrines of the metamorphism of the crystalline rocks and their Paleozoic age. With the determination of the anticlinal attitude quite a different interpretation of age resulted, as well as less respect for the theories that had led my masters astray.
A word in reference to the determination of this structure. C. B. Adams in his Annual Reports (1846-8) states the ques- tions at issue in respect to the age of the crystallines, without endorsing either view. Having noted the existence of quartzite and limestone in Plymouth upon the east side of the range, he queries whether these rocks may not be repetitions of the gran- ular quartz and Stockbridge limestone. Other facts show that Adams favored the metamorphic view—and it is supposed influ-
50 Gy Lah Lal INCI C OES
enced his successor Zadock Thompson to draw up an elaborate section along the Winooski River between Burlington and Water- bury, exhibiting a fan-shaped stratification. After taking charge of the Vermont survey, my father commissioned me to measure and protract on paper the thirteen general sections across the state. From these plans he drew various conclusions, including the anticlinal attitude of the Green Mountains, without referring either to his theoretical Hoosac section of 1847, or to the Cana- dian belief in a synclinal, or to its importance in the development of the more eastern terranes. Since 18617 I have several times insisted upon the fact and its importance, maintaining at first that Logan’s description of Sutton Mountain favored the anti- clinal view. Selwyn corrected Logan’s error in 1877. Professor Dana acquiesced in this view in 1882. Of late it has been con- firmed by Professor Pumpelly? for the Hoosac Mountain, and by Mir Gol Whittles tor themrange abel itm toll. ne Att amyaeiinet visit to Montreal (1857) Sir W. E. Logan referred the chief part of Canada adjoining Vermont to the Oneida conglomerate. After 1860 he devised the ‘‘Quebec group,” subdivided into the Levis, Lauzon, and Sillery formations, supposed to be allied to the Calciferous and Chazy. It was his coloration of the maps next the international boundary, classified into these three divis- ions, that I copied on my map of New Hampshire as part of the Huronian, or the hydro-mica schists. In my first two annual reports I used the name of Quebec for these rocks, changing later at the instance of Dr. Hunt, who claimed them to be partly, at least, older than Cambrian, or equivalent to the Huronian of Ontario. Our use of terms was dependent upon the terminology employed by our Canadian neighbors, as they were the origina- tors of the various expressions employed. Still another modif- cation of the nomenclature will be presently alluded to.
Topographical results —TYhe map in our atlas was drawn upon
Geological sections across New Hampshire and Vermont, Bull. Am. Mus., N. Y., Wolk ly, nev
2 Geology of the Green Mountains in Massachusetts. Monograph XXIII. of the
Wo So Ge So 3 JOURNAL OF GEOLOGY, Vol. IL., p. 296.
GEOLOGY OF NEW HAMPSH/TRE Si
the scale of two and one-half miles to the inch, to match the Massachusetts work of Simeon Borden in 1842, adding to his. delineations approximate contours for every hundred feet. It was based upon the United States government map of the inter- national boundary (1842), special triangulation under our direc- tion, the early and late determinations of the United States coast and geodetic survey, combined with detailed compilations from the county odometer road surveys. Without pretense to special merit, it has been pleasant to us to compare the best parts of this map in the White Mountains and the southeast part of the state with the beautiful sheets of the United States geological survey,. when enlarged to their scale. That experts should at first have placed higher value upon this map than it deserved is not the fault of its compilers.
DETERMINATION OF THE ORDER OF THE GROUPS OF SCHISTS.
In establishing the New Hampshire stratigraphical columm the attempt was first made to construct it independently of the existence of similar rocks elsewhere. Certain principles were accepted as well established. One of them was that crystalline schists constitute stratified formations, capable of being identified in different districts by their mineral composition. Among the groups capable of ready recognition were the following: gneiss,. ordinarily consisting of the three constituent minerals, quartz, feldspar and mica, with no accessories; and this was termed com- mon, or from a locality, Lake Winnipisoegee gneiss. This for con- venience was shortened to Lake gneiss, and seemed to be equiv- alent to the lower part of the Green Mountain series. In another area mica was replaced by chlorite, giving rise to chloritic gneiss,. protogene or locally Bethlehem gneiss. Another peculiar variety was termed Porphyritic, corresponding to the Augengneiss of Cen- tral Europe. The occurrence of large crystals of feldspar seemed to be more noticeable than the presence of black spots with the white, producing a resemblance to eyes. It was also found that sometimes this porphyritic rock was devoid of foliation—the crystals were disposed at random instead of being arranged in
52 Co. tal HM I CIM EC OCI
lines—and our observations were never extended so far as to be able to declare that these differences were of importance.
Of the mica schists one range abounded in /fdrolite, a second in andalusite, and a third in staurolite. No two of these minerals were combined in the same set of schists, while all the bands are related to one another. The hydro-mica-schist group contained associated bands of chlorite schist, quartzites, bedded diorites, diabases and protogenes; and had before our time been known as ‘‘talcose slate.’’ No local term was applied to this complex, as it was supposed to represent the Huronian group of Canada, with which it had strong points of resemblance. Hornblende-schist proved to be common, and, with some misgiving, was relegated to the base of the hydro-mica groups. These several groups of schists were believed to belong to as many distinct periods of growth, each with its peculiar conditions.
Inasmuch as the formations possessed northerly trends, sec- tions in east and west lines would most economically represent their structure, and hence the Dartmouth museum has a special large case prepared upon which fifteen sections are arranged in geographical order extending from Maine to New York across New Hampshire and Vermont. This collection contains about 3000 specimens, which are still further elucidated by geologically colored profiles and a large relief map.
A second principle employed was the discovery that the crys- talline schists of New England tended to assume ovoidal shapes exhibiting a banded structure. Reference was made to the groups of Percival in Connecticut, K,, K,and K,, as well as to the B of the Eastern Primary. The center of the oval seems to be the oldest part. Dr. A. C. Lawson* describes similar areas in the Rainy Lake district north of Lake Superior, as does Professor A. Winchell? in Minnesota and Professor B. K. Emerson in western Massachusetts.
As there is no readily recognizable base to the New Hamp- shire rocks, it was found necessary to fix upon some convenient
t Ann. Rept. Geol. Can., 1887.
2 Bull. Geol. Soc. Amer., Vol. I., p. 361. 3 [bid., p. 559.
GEOLOGY OF NEW HAMPSHIRE 53
starting point where the succession seemed obvious. The hori- zon selected was the superposition of hornblende-schist upon gneiss. My first work of a stratigraphical nature had been the study of a low anticline of this nature at Shelburne Falls, Mass." At the base was a well defined gneiss, capped in succession by hornblende-schist, mica-schist and the same with interbedded limestones.* The first two rocks occupied quite a small area, and were exposed only through denudation. On proceeding nor- therly similar relations of gneiss and hornblende-schist were seen upon several of our sections. Hence the generalization, horn- blende-schist overlies gneiss. The next point was to follow out the distribution of these two rocks. The gneiss of the Halifax- Hartland range proved to bea well-defined geanticlinal sixty miles long, dipping westerly to reappear in the Green Mountain gneissic area, and dipping easterly to reappear in the gneisses of Cheshire, Sullivan and Grafton counties, traceable for over one hundred miles with a westerly dip. On traversing the country to the east still other gneisses appear. Hence the second generaliza- tion, there exist several parallel anticlines of gneiss, connecting the Green Mountain and Lake areas. But twoof these ranges cover an area of porphyritic gneiss, between Jaffrey and Groton, sixty miles in length, thirteen miles in its greatest breadth, following the height of land between the Connecticut and Merrimack rivers. Its stratification is obscure, while the representation of the dips upon the six revised sections crossing it, conform to the notion of its inferior position. Nothing has been found underlying this rock, so that it must be considered as the base of the crystalline succession for New England. More than twenty patches of this basal gneiss occur in the state, a few carrying fibrolite schist and one contains fragments of a dark gneiss—possibly an older layer.
The place of the chloritic (Bethlehem) gneiss is not so readily determined. It occurs only on the east slope of the Connecticut
*Proc. Boston Soc. Nat. Hist., Vol. VI., p. 330.
? Upon the Hawley sheet Professor Emerson describes the same succession, using the local names, Becket gneiss, Hawley amphibolite, Goshen schist and Conway schist.
54 Co Lal EIN CTE COCIE
Valley in six or eight isolated areas, interspersed over a distance of a hundred and twenty-five miles, and covered by hornblende- schist occasionally. It has been located between the porphyritic and lake gneisses. The hornblende schist does not guide us satisfactorily to the upper formations; and hence other consid- erations must be taken into account in the further attempts at ‘classification. Most of the remaining rocks are some form of ‘mica schist. They are plainly above the gneisses, for wherever any of them come in contact with the feldspathic rocks they are superincumbent. They have been distinguished as the Montalban, or mica schists carrying some feldspar with fibrolite or andalusite; the group of hydromica schists; Rockingham mica schists; Mern- mack group and Ferruginous slates. After detailed studies our conclusion was that the Montalban preceded the hydromica schist ‘which were closely related to the Kearsarge and Merrimack -schists and the Ferruginous slates of Hillsborough county. The -Rockingham schists simulated the Montalban.
The hydro-mica schists are arranged primarily in two diver- gent lines, which are assumed to represent one grand formation, whatever its place in the scale may be. The best known is that \which starts in western Massachusetts under the old name of italcose schist, passes through central Vermont east of the Green -Mountains and continues past Quebec parallel to the St. Law- :rence River. Both the Vermont and Canada surveys recognized a similar (third) belt on the west side of the Green Mountains, extending as far south as Middlebury. The eastern line begins at Bellows Falls and is nearly continuous along the Connecticut to tthe mouth of the Passumpsic River, and thus expands to as great a width as that of the central belt, and it continues through the western edge of Maine into the Gaspé peninsula. iRanges of gneiss flank both these hydro-mica belts, viz., the «Green Mountain gneiss upon the west and the Connecticut band .of lake gneiss on the east, and with the same synclinal disposi- tion. Inside of the hydro-mica schists are belts of argillite, which seem to follow the same synclinal law of distribution. “There is left between the argillites an immense area which has
GEOLOGY OF NEW HAMPSHIRE 55
been designated the Calciferous mica schist, and it naturally completes the filling of the basin. This is the formation that was described in my Shelburne Falls section in 1858, with the same two divisions. There is a great development of rocks related to the lower division along the Connecticut Valley that were presumed to represent the lower part of the Calciferous, and they received the name of Coés group, consisting of a basal quartzite, mica- schists, hornblende-schists, staurolite-mica-schists and _ slates, several thousand feet in thickness. The early Canadian reports regarded the Calciferous schists as of Niagara age. Our report regards all these schists as the most modern of the stratigraph- ical column, but does not insist upon their identity with the beds carrying fossils.
An important chapter would relate to the discovery of fos- sils in New Hampshire. They were found at Littleton in 1873 and referred to the Lower Helderberg by E. Billings, paleontol- ogist to the Canadian survey. Later discoveries have proved the Niagara age of the enclosing rock, because of the presence of Halysites or chain coral and Pentamerus nystus. The rocks connected with the fossils are limestones, slates and sandstones, more like the Coéds bands than the Calciferous. They have been followed down the Connecticut to connect with the fossil- iferous limestone and sandstone of Bernardston, Massachusetts, belonging to the Devonian. Niagara fossils are also known from the west shore of Lake Memphremagog.
The column thus established from structural evidence con-
sists at the base of the porphyritic or Augengneiss followed by the Bethlehem or chlorite gneiss, and the ordinary lake gneisses, amounting to at least 28,000 feet in thickness, if foliz are to be esteemed capable of measurement. In the view of the report, the immediately ensuing 12,000 feet of gneissic-mica schists or Montalban occupied an intermediate place between the gneisses and the hydro-mica-schists. These last were subdivided in the Connecticut belt into the Libson chlorite schist, the Lyman argillitic (Urthonsclefer) schist and the auriferous conglomerate, in all 12,000 feet thick. In the central belt the triple classifi-
56 Co Jal, Jalil OSHC OCI
cation of Logan into the Levis, Lauzon and Sillery was recog- nized. In the central and southern part of the state was a great development of mica-schists of about the same thickness, called locally the Rockingham, Kearsarge and Merrimack groups. The well recognized Paleozoic rock of the northern parts of the state foot up about 16,000 feet, and were named the Cambrian slates, Cods group, Calciferous mica schist and the Lower Helderberg.
Correlation with recognized standards.—Having established an order of succession, our next effort was directed to their correla- tion, with the generally recognized sequence elsewhere. In Canada the order was that of Laurentian, Labrador, Huronian and Cambrian; in southern New England no satisfactory deter- minations were available. The porphyritic gneiss naturally allied itself to the Augengneiss of the Laurentian of Canada and else- where. The Bethlehem gneiss had more affinities with the same group than any other; and we were fortified in our conclusions by the independent and unsolicited opinions of Professor J. D. Dana and Dr. T. Sterry Hunt. It was difficult to know where to place the lake gneiss, if not in the same general group. The Manchester and Berlin ranges rendered this reference easy because of their saccharoidal character. Other areas contained beds of magnetite, limestone and plumbago, but none of the Adirondack pyroxenic rocks occurred in any of them. Hence, the three schistose*groups would seem to correspond in general with the Ottawa and Grenville divisions of the Canadian Lauren- tian. While referring the gabbros to the Labrador system, it was expressly stated that they could be regarded only as an igneous rock, and hence not properly a stratified system.
If these gabbros represented an igneous action occurring in the later Laurentian of Canada, then the schists penetrated by them in New Hampshire must have been equally ancient or Archean. Hence the origination of the term d/ontalban, representing a ter- rane younger than the Laurentian and older than the Huronian.".
t This does not correspond to the signification attached to this word later by Dr. T. Sterry Hunt.
GEOLOGY OF NEW HAMPSHIRE 57
As thus defined the New Hampshire Montalban is like the Coutcliching division of Ontario, proposed by Professor A. C. Lawson for a system that occupies just this horizon.
The hydro-mic-aschists and associated diabases, etc., corre- sponded well petrographically to the Huronian complex, and were so referred. At first it was thought that our White Mountain porphyries might be referred to the lower Huronian or Arvonian of Dr. Hunt, but the reasons demanding the removal of the gab- bro from the stratified systems prevailed equally well as applied to the porphyries.
As to the various mica-schists and related rocks, called locally Kearsarge, Merrimack and Rockingham, no satisfactory reference could be made; and hence they were called Paleozoic in general, their alliance being obviously Huronian or Cambrian. The argillites were all referred to the Cambrian, having in mind the fact that this seemed to be the place for rocks of this class, whether in Vermont (Georgia), Massachusetts (Braintree), or Nova Scotia. The Coéds quartzites, schists and slates, also the Calciferous mica schists all received an assignment to horizons superior to the Cambrian.
An improved classification.—The question now arises, How can our early classification be improved? It is eighteen years since the New Hampshire report was published, and there are many new workers in the field, all placing great reliance upon petro- graphical principles, such as were inaugurated in Dr. Hawes’ report. Some are advocates of extreme metamorphism, and hence the conclusions are not harmonious. It seems to us that our early views may be modified by the following principles: (1) The mineral characters of crystalline rocks are not a sure guide to geological age. (2) Protogenes, diabases and diorites more or less interstratified with hydro-micas are of true igneous origin. (3) The Archean gneisses and protogenes may also be of igneous origin, and their apparent stratification has no con- nection with sedimentary or chemical deposition. (4) The Huronian* era may properly represent the beginning of sedi-
* There seems to be no need of introducing a new term—Al]gonkian — to replace
58 C. H. HITCHCOCK
mentation. The first sediments must have been accompanied by a greater flow of eruptives than those formed later. (5) Much of the hornblende-schist is igneous, related in origin to lacco- lites. (6) Serpentine and steatite are alterations of material orig- inally igneous.
Applying such principles to the classification of the. rocks of northern New England, we may improve on the report in sev- eral particulars. (1) Archean rocks are not eliminated from our list. They exist as oval areas, such as have been indicated, in the Stamford gneiss and south of Mt. Killington, Vermont, in the Hinsdale, Massachusetts, area, the Hoosac Mountain, and elsewhere. I recognize the porphyritic gneiss in the Stamford rock and in the Hoosac tunnel as Archean. (2) Our hesi- tancy about the place of the Bethlehem gneiss is met by recent observations. They are batholites, containing inclusions of the adjacent mica schists. It does:not follow that all these proto- gene areas are of the same character; each one must be studied by itself. Some may be altered gneisses, and others sandstones where feldspar grains prevail. (3) Later observers are not agreed as to the nature of the upper part of the Green Mountain gneisses. What is apparently the same material is called ‘‘ Cam- brian gneiss’? on Hoosac Mountain by Professor R. Pumpelly* and ‘“‘Algonkian” by Mr. C. L. Whittle? near Rutland, Vermont, Professor Emerson in adopting Pumpelly’s view finds a series of anticlinals of the same material further east, which probably correspond to the similar folds referred above to the lake gneisses. (4) Later conclusions respecting the age of the rocks entering Vermont and New Hampshire are entertained by the Canadian Geological Survey. There are three areas of pre-Cam- brian, viz., the axis of the Green Mountains; the Sherbrooke belt, reaching Lake Memphremagog, and along the international Huronian. Better amend the latter so as to exclude the Cambrian, rather than cumber literature with a term harder to write, less euphonious, and with practically no differ- ence of signification.
Monograph XXIII., U.S. Geol. Survey.
2? This JOURNAL, Vol. II., p. 396. 3 Bull. Geol. Soc. Amer., Vol. L., p. 453.
GEOLOGY OF NEW HAMPSHIRE 59
boundary of New Hampshire and Maine. Associated with these older rocks are slates, sandstones and conglomerates believed to be Lower Cambrian. The continuations of the Calciferous mica- schists are termed Cambro-Silurian, because Trenton-Utica grap- tolites occur in them. Various limited outlying patches of Upper Silurian fossiliferous rocks rest upon the mica-schists. It is easy to connect these belts with their more southern devel- opments. Some portions of what we have called Huronian are Pre-Cambrian, in the two diverging areas specified above, page 54. The two bands of argillite supposed to overlie the hydro- micas, the one reaching to Barnard and the other to North Hartland, are identical with the Cambrian of Ells, and there is complete agreement as to the order of succession of all the formations named between the two surveys. This argillite underlies the Calciferous mica-schist. (5) In this connection it is proper to say that recent studies enable me ‘to trace the argillite of Bernardston, Mass., past Bellows Falls to East Hanover and Orford, and it is to be distinguished from the two ranges just named in Vermont, for it overlies the Calciferous, and is associated with the latest rocks of the Connecticut Val- ley, being perhaps Devonian. I have recently explored a mass of it in Littleton, N. H., which appears to overlie the Niagara. It was called Cambrian in part in the New Hampshire report, because it seemed to be the same with the slates of that age further west, while other portions carrying incipient stauro- lites and small garnets were denominated Coés slate. (6) A study of several areas of hornblende-schist proves that they are igneous. (7) The area of the Montalban about the Presidential range among the White Mountains proves to be less in amount than has been stated. Mts. Adams, Jefferson and even the top of Mt. Washington are composed of mica-schists like those occurring along the carriage road rather than the true gneisses. On Mt. Clinton the mica-schists carry fragments of other rocks as if they were an igneous paste carrying inclusions.
60 Ga tel JANIE CAC OOK
SURFACE GEOLOGY.
Few of the early state reports have discussed glacial phe- nomena so fully as that of New Hampshire. The glacial theory of Agassiz, and Dana’s doctrines as to the origin of the modified drift in connection with the flooding of river valleys through the melting of ice were accepted to explain the facts obtained. Measurements of strie were taken everywhere, whether upon the tops of mountains, scant forest exposures, or in valleys, their number much exceeding those taken by any other organ- ization.t The most important conclusion derived, for which the territory is best adapted because of the great elevation of the land, is that during the maximum ice development the motion came from the northwest and was directed over the mountains ~ southeasterly; or, in other words, from the St. Lawrence Val- ley up the northward slopes of the White and Green Moun- tains, and over them towards the Atlantic.2 Striz were noted upon the summits of nearly all the highest mountains, and where these were wanting transported erratics abounded. Later observations have shown some form of glacial work upon every summit and every col of the White Mountains. By way of confirmation of this doctrine, our latest unpublished observa- tions show that remnants of the accompanying terminal moraines3 had a northeast-southwest course, being at right angles to the normal direction of the ice-sheet. In other parts of the state, notably upon the seaward slope, the striae appear to have been deflected by the topography; and still later evidence is pre- sented to suggest the presence of local glaciers radiating in every direction from the higher mountains, pushing northerly and northeasterly into Canada as well as to the south. A few sug- gestions as to the diversity of the Ice Age were made, such as would now confirm the theory of Geikie. They consist in the advocacy of interglacial deposits in the valley of Lake Winni- piseogee and about Portland, Me., and in the existence of an
tSeventh Annual Report of the U. S. Survey, p. 157.
2 Bulletin Geol. Soc. Am., Vol. V., p. 35. 3 Procy Amen.pAwyA. TS CleflVOloXclleanpaeki7/3%
GEOLOGY OF NEW HAMPSHIRE 61
abnormally compact lower till under the ordinary ground moraine.
The writer can find no reference to the drumlins earlier than his own descriptions of Prospect Hill* in Andover, Mass., in 1867. It represented something accumulated by ice, but not an ordi- nary moraine. These hills received much attention in the report, hundreds of them having been mapped in theatlas. Their longer diameters were found to coincide with the direction of the ice movement ; being generally southeasterly in Rockingham county, southerly west of Merrimack River, and west of south in the Connecticut Valley on the edge of Massachusetts. Mr. Warren Upham devoted himself to the exploration of these lenticular hills, and in searching for them beyond the limits of New Hamp- shire, became interested in the terminal moraines of Cape Cod and Long Island.’
Special attention was given to the modified drift in the report by Mr. Upham. The terraces of the Connecticut and Merrimack Valleys were carefully mapped and leveled, with the intention of testing the application of the marine or fluviatile theory of their origin. It would appear that the highest terraces and deltas of tributaries represent the remnants of the ancient flood plain where the river had its greatest volume. These remnants are quite uniformly nearly two hundred feet above the Connecticut River— whether at the state line on the south or at the mouth of the Pas- sumpsic. Very commonly a tributary increases the height of the flood plain forashort distance. If the terraces had been made in a series of lakes, or at successive heights of the ocean, they should have been arranged in a series of steps from the sea upwards.
Eskers had been described in Maine, but it remained for Mr. Upham to bring them to light in all the principal New Hampshire valleys, especially in the Connecticut from Windsor, Vt. to Lyme, N. H., a distance of thirty miles. The main river cuts its way across this gravel ridge seven times, and it is quite concealed by terrace deposits in a part of its course.
* Proc. Essex Inst. Nat. Hist., Vol. V., p. 159.
? Geol. New Hampshire, Part III., p. 300.
62 Co. tale PANIC OO CIE
The writer in accepting the diversity of the Ice Age, believes the Champlain to have been one of the glacial epochs. The name was originally given by him to the sands and clays bearing marine mollusca, with the accompanying deltas and terraces ; and that includes terraces in the Champlain Valley, the south-flowing rivers and along the New England coast. The fossils indicated a glacial climate as far south as Massachusetts Bay, and a cooler climate in Nantucket. It was atime of differential depression, amounting to more than one foot to the mile in proceeding north- ward, so that sediments filled up rivers and compelled the renewed streams of today to find new channels for themselves over ledges. With a submergence of perhaps a thousand feet in the lower St. Lawrence and an arctic climate, glaciers would form - on the Laurentides, Green and White Mountains, moving towards each other and discharging icebergs into the inter-island area. Mr. Upham* suggests that all the drumlins in the country were formed at this time. It was certainly true of those near Boston, as they contain not less than fifty-five specimens of marine tem- perate mollusca, which must have been transported as erratics to their present locations. Hence the climate of New England must have had an arctic character in the Champlain epoch.
As elsewhere suggested,? the writer believes the adoption of the view that the Champlain was a glacial epoch with the land much depressed, and a sea full of icebergs moving southwesterly from the Gulf of St. Lawrence, will enable the advocates of the glacier and iceberg theories to harmonize their conflicting opin- ions.
(Es ll, Inliarenieoeix.
12 Bull. Geol. Soc. Amer., Vol. VII
NORTE AMERICAN GRAPD OLIMIES':
NEW SPECIES AND VERTICAL RANGE."
PREFACE.
No general revision of American graptolites has been attempted since the termination of Hall’s classic labors some thirty years ago, and one based on the lines of recent taxonomic progress is badly needed. The present paper is a preliminary attempt at such a zoGdlogic and geologic revision.
The tables showing the vertical range of species are, to a considerable extent, based on my own determinations. This reservation is necessary, as many of the ranges assigned to species are incorrect, the result of erroneous identification. In this matter I am glad to find myself in general accord with Ami,’ almost the only American observer who has studied extensively the graptolites in the light of recent foreign work.
A word as to the somewhat numerous changes made in the synonymy. Most of them are in accordance with general grap- tolite consensus. Most of the remainder are explicable on the ground of priority. Ina previous paper3 I followed general con- sensus rather than attempt the necessary thorough overhauling of the synonymy, reserving the latter until such time as I could publish more extensively the reasons for the requisite changes. Now, however, it seems best to enforce priority rigidly, and to this end the original spelling has been followed in all cases. Reasons for deviation from current usage are given in brief, but in a paper of this compass it is of course not possible to give the evidence in extenso.
No attempt has here been made to determine accurately the
* Published by permission of the Director of the U. S. Geological Survey.
2 Bull. Geol. Soc. Amer., II., pp. 477-502, Plate XX.
3Ann. Rep. Geol. Surv. Ark. for 1890 (1892), III., pp. 401-418, Plate IX. 63
64 BR, ®, CURLEY
zodlogic limits of the group, as this paper being rather geologic than zodlogic, the aim has been to include every species of grapto- lite (as the word is generally understood), reported from Ameri- can strata, with the proper generic reference and the ascertained range. Only species in good standing are, however, given, and such forms as Nereograpsus, which are no longer regarded by any one as graptolites, are omitted.
Finally, all new species here described will be fully illustrated in a future publication of the U.S. Geological Survey. The authority for each new species is appended to it.
In DESCRIPTIONS ORNGENE RAVANID ESP Ee Glizs: PHYLLOGRAPTUS HALL, 1858.
Rep. Progr. Geol. Surv. Can. for 1857, pp. 135, 137. Type, P. typus Hall. Phyllograptus ? cambrensis Walcott, sp. nov.
“ Diplograptus simplex (Emmons) Walcott, 1886, Bull. 30, U. S. Geol. Surv., pp. 92-93, Plate XI., Figs. 4, 4a; “Phyllograpius simplex (Emmons)” Walcott, 1889, Amer. Jour. Sci., XXXVIII., p. 388.
The synonymic relations of this species are very complex. For the pres- ent it is sufficient that it is neither /zcoides simplex Emmons, 1844 (Zaconic System, p. 27, Plate V., Fig. 1), nor Diplograpsus secalinus (Eaton) Emmons, 1856 (American Geology, |., Part II., p. 104, Plate I., Fig. 11).
BRYOGRAPTUS LAPWORTH, 1880. Ann. and Mag. Nat. Hist., V., p. 164. Type, B. syerudfi Lapw.
Bryograptus ? multiramosus Gurley, sp. nov.
Polypary round-triangular in outline; length and breadth each 20™™. Proximal extremity bearing a sicula 1™™ long. Branches numerous, dividing dichotomously, one being five times divided (including sicular division). Thece 30 to 35 in 25™™, forming cylindrical tubes, free for one-half their _ length or a little less, pustuliferous. Virgula not seen.
Horizon and locality.—Several specimens on some pieces of Upper Cambrian shale from Matanné, Canada, sent by Sir J. William Dawson to the National Museum.
DICHOGRAPSUS SALTER, 1863.
Quart. Jour. Geol. Soc. London, XIX., p. 139. Type, D sedgwtck Salter. Dichograpsus remotus Gurley, sp. nov.
Only a single specimen seen. Branches very narrow, having a length of 25 to 35™™ between successive points of division, the latter apparently becom-
NORTH AMERICAN GRAPTOLITES 65
ing progressively more remote from one another. Thecz not well shown, about 25 in 25™". The main characteristic of this species is the remoteness. of the points of bifurcation and the small size of the branches.
Horizon and locality.—Calciferous shales (zone with Dichograpsus flextlis, etc.), Point Levis, Canada.
Dichograpsus abnormis (Hall).
Herrmann’ regards this species as simply an ‘‘abnormal” specimen of D. rigidus. \ am unable to agree with this view, the species apparently being well characterized.
TETRAGRAPSUS SALTER, 1863. Quart. Jour. Geol. Soc. London, XIX., p. 140. Type 7. cruczadzs Salter..
Tetragrapsus acanthonotus Gurley, sp.nov. Plate IV., Figs. 1, Ia.
Width of branches from apex of thece to virgula, 2.5—3™™. Dorsal mar- gins at intervals of from I to 3 thece (generally opposite every other theca): bearing spines 1™™ or less in length, which are integumentary processes, not connected with the virgula. Thece 17 to 20 in 25™™, slightly curved with. the upper lip produced into a rather acute denticle. Line of aperture con- cave, inclined (on distal side) to virgula about 120°.
Horizon and locality.—Calciferous shales about one and one-quarter miles: N.N.W. of the East Railway Station, at Point Levis, Canada, opposite the iron foundry. '
Recognizable at a glance by its spinose dorsal margin. The generic ref- erence is made from a single small specimen seen.
DiIDYMOGRAPSUS McCoy, 1851. . Brit. Palaeozoic Fossils, p. 9.
Didymograpsus bipunctatus Gurley, sp. nov. Plate V., Figs. 7, 7a.
Sicula slender, short. Branches diverging from sicula at an angle of 110°, very slender, with an undulating dorsal margin, each undulation correspond- ing toa theca. Thecze about 65 in 25™™", curved, equally wide throughout, with the apertural margin straight, and retrotruncate. Between each pair of thecze are two “pustules” (one at base of proximal theca, the other near its distal end), appearing as though joined by an elevated line. Owing to the close proximity of the series of elevated lines, the specimens, viewed in some directions, appear to possess a continuous undulating raised line.
Horizon and locality.-—On a slab of Calciferous shale in a small collection from one mile N.W. of the East Railway Station, Point: Levis, Canada. A dozen specimens, mostly small or immature, were seen.
«Nyt Mag. f. Naturvid, 1885, XXIX., p. 210.
66 Vie Ines (GOT ESE NG
From all species of the genus except two or three, this species is distin guished by its small size. From the remainder by the undulating dorsal mar-- gin and the double series of “ pustules.”
Didymograpsus perfiexus Gurley sp. nov.
Branches diverging from a minute sicula at a variable angle, probably from 225° to 270°, variously directed subsequently from post mortem deflec- tion, gradually widening from their origin to a maximum width of 3™". Maxi- mum length observed (in a specimen whose width showed that it was situated far to the proximal side of other fragments, and that it could not have been near the sicula) 17. Coenosarcal canal narrow, occupying not more than one-quarter or one-fifth of the extreme width of the branch. Thece 20 to 25 in 25™™, almost or quite straight, very wide in proportion to their length, little wider (one-quarter or thereabouts) at aperture than at base; inclined to axis of branch about 30°; apertural margin straight, destitute of spines, obliquely directed,
Horizon and locality.—Upper Calciferous shales, Summit, Nev.
This species presents itself under very many aspects, so many in fact that I shave several times suspected that two species were present. Subsequent study chas, however, led to the conclusion that probably all these formsare to be referred to differences in preservation conditions, that is that they are preservation facies. To start with the angle of divergence varies within very wide limits, being at one extreme about two, and at the other about three right angles. Several intermediate positions are present. The true angle was probably mearer the upper than the lower limit, the lowering resulting from subsequent (post mortem) bending of the slender polypary. This seems not unreasona- ble especially when the inclination of the theca in some specimens is less than the average, and these same thecz have every appearance of having been compressed backward against the virgula. Such pressure naturally tends to diminish the angle of divergence, measured as the latter is on the dorsal side. These two conditions (diminished angle and flattening of thecez) were not, however, observed on the same specimen. ‘The inclination of the thecz to the virgula (measured of course, on the distal side), seems to increase slowly, those on the distal portion being somewhat moreerect. They are also slightly more numerous ir a given space. Upon each theca at the distal corner remote from the virgula, is a circular pustule-like body which may have been an orifice in the lateral wall.
This form probably approaches D. uzcholsont Lapw., and D. suecicus Tullb., more nearly than any others. The thece here are rather regularly 22 to 24 in 25™™ as opposed to 25 to 30 (average 26) in the same space, in Lapworth’s species. Also D. xicholsonz differs in the somewhat rigid branch ‘with a uniform width of about 1™™.25, and the concave thecal mouth usually prolonged into a denticle. With DY. swectcus its affinities would seem even
NORTH AMERICAN GRAPTOLITES 67
closer, but in that species we have somewhat crooked theca, twice or one and one-half times as wide at mouth as at base, with the somewhat concave mouth often bearing a denticle.
Didymograpsus geminus (Hisinger). (Miller’s North American Geology and Paleontology, 1889, p. 186, Fig. 169.)
Concerning this form, it may be remarked (1) that Hisinger’s gemznus (Lethaea Suecica, Suppl. 2, 1840, p. 5, Part XXXVIII., Fig. 3) is a syno- nym for D. murchisont Beck (Murchison’s Sz/urzan System, Part I1., 1839, p. 694, Plate XXVI. Fig. 4); (2) that D. murchisoni is not known to be Ameri- can (except as var. furcillatus Lapw.; see p. 4); and (3) that the original of Miller’s figure is Carruther’s mal-identification (in Murchison’s Sz/urza, 4 ed., 1867, Plate IV., Fig. 8)as D. geminus His., of D. fatulus Hall.
Didymograpsus hirundo Salter, 1863. Quar. Jour. Geol. Soc. London, XIX., p. 137, Fig. 13.
Graptolithus constrictus Hall, 1865, Can. Org. Rem., Dec. II., p. 76, Pilate). ies. 23-277.
This species is very largely represented in collections from the main Point. Leviszone. The supposed constriction of the theca mentioned by Hallis clearly an illusion, due to the intervention of a thin film of shale which covers one theca along the furrow produced by the overlapping apertural margin of the next proximal theca. This produces an appearance as though the distal theca were interrupted and contracted to receive the next proximal one. Specimens in relief show the thecze uncontracted.
Didymograpsus convexus Gurley, sp. nov. Plate V., Fig. 8.
Branches slender, in distal portion 1™™ wide, diverging from a small sicula with an upwardly concave-rounded curve, including between them (on the dorsal side, of course) an angle of about 265°. Thece 20 to 22 in 25™™, inclined to axis of branch 25° to 30°, widest at mouth, with a straight, aper- tural margin; the last making (on the distal side) an angle with the virgula of 105° to 110°; thecze free for one-half their length.
Only two specimens were seen, but the aspect is such that they cannot be referred to D. serratulus or any other described species. Possibly it may be the proximal portion of D. sagztticau/is, but nearly fifty years have passed since the discovery of that species without the finding of any specimens long enough to connect the distal and proximal parts; hence the necessity for two names, at least pending the proof of such a connection which may be long delayed.
This species may be recognized by the broadly rounded curve at the base.
Horizon and locality—Lower Dicellograpsus zone, Stockport, N. Y.
68 Ike dk, (Ge WIRILIE NZ.
Didymograptus sagitticaulis Gurley, sp. nov. Grapiolithus saeditariusy (iiss) ElaillPallNeavien OA, s,m ane 2 mei Fig. 1; ‘“ Graptolithus sagittarius Hall (non-His.),” etc., of subse- quent writers; Didymograptus sagittarius Hall, Lapworth, 1886, @rans. Roy. Soc. Can, Vi;, Sect. IV, pp. 1s0—-181, 163-164"
This name is proposed to clear the synonymy. No name has ever been given to this species, that under which it has gone being derived merely from the erroneous identification of it with Hisinger’s species. Very possibly the species is a distal fragment of one of the others in the same beds, but if so, it is so far distal that the chances of connecting it with the proximal portion are rather small, in the meantime it is important that it have a name in good standing, especially as, being a very common form, it occurs in nearly every list of species from the Lower Dicellograpsus zone, and usually appears under some clumsy explanatory circumlocution.
Horizon and locality.—Lower Dicellograpsus zone.
STEPHANOGRAPTUS GEINITZ, 1866. Neues Jahrb. fiir Mineral., 1866, p. 124. . Type, S. gvaczlzs (Hall).
This generic name takes precedence of /felzcograptus Nicholson,* and Coenograptus Hall,? both of which were founded upon the same species (Grap- tolithus gractlis Hall).
Stephanograptus crassicaulis Gurley, sp. nov.
Specimen resembling one-half of S. gvacz?zs but with a much thicker main curved stem and branches, the former measuring from 0.50 to 0.75. in thickness, the latter inthe distal portions attaining a width of 1™™. The branches are given off from the main stem at first at a right angle, but with each succeeding branch the divergence becomes less. The thece on the distal portion of the branches measure 20 in 25™™.
Horizon and locality.—Lower Dicellograpsus zone, Stockport, N. Y.
This species differs from all other of the genus in its very stout polypary. Though only one-half of the polypary has been seen, the generic reference seems hardly open to doubt so much does the habit of the species resemble that of S. gracilis.
Stephanograptus extlis Lapworth, sp. nov.
Polypary bilaterally symmetric, consisting of two simple (or compound) monoprionidian branches about 40™™" long, diverging in opposite directions from the center of a minute radicular bar; branches bearing thece of type of those of S. evacz/is Hall. Width of branches at origin about o™™.17, pro- ceding outward at first horizontally (180°), the deflection increasing, however,
t Ann. and Mag. Nat. Hist. 1868, IL., p. 23. 2 Twentieth Rep. N. Y. St. Cab. Nat Hist., 1868, p. 179.
NORTH AMERICAN GRAPTOLITES 69
at end of first theca to 240°; branches continued in a gentle, flexuous curve to their extremities, averaging in width about 0.5. Thecz 30 or 32 in 25™™; adnate to the coenosarcal canal, with straight or very slightly convex margins and slightly inclined apertural edge.
The affinities of this form are distinctly with S. fertenuzs Lapworth and its associates, S. exflanatus and S. nttidulus. From all these, however, it differs in absence of secondary branches and in general form of polypary.
Horizon and locality.—Lower Dicellograpsus zone, Stockport, N Y.
To the above description I may add that some specimens indicate that the primary branches give origin to secondary ones, probably from the athe- caphorous margin.
AZYGOGRAPTUS NICHOLSON, 1875. Ann. and Mag. Nat. Hist., XVI., p. 269. Type, A. dapwortht Nich. Azygograptus? walcotti Lapworth, sp. nov.
Polypary unilateral, monoprionidian, consisting of a single flexuous and simple compressed branch proceeding almost horizontally from the side of an inconspicuous sicula, 50 to 75™™ in length, in average diameter about 0.5™™. Thecz 16 in 25™™, without overlap, consisting of conical tubes, increasing slightly in diameter throughout, adnate to the coenosarcal canal, with straight or slightly convex ventral margins. Apertural margin a little inclined and projecting from the ventral margin for a distance equal to about one-half the diameter of the polypary and transgressing upon the periderm for a similar distance. Denticle almost rectangular; excavations and interspaces shallow and inconspicuous.
Horizon and locality.—Lower Dzcellograpsus zone, Stockport, N. Y.
This form has all the appearance of belonging to the curious genus Azygograptus. "Two specimens occur in the collection. One lacks the prox- imal part; in the other there is evidence of the unilateral nature of the polypary and of the presence of the sicula. Further research may show that it belongs to the bilateral genus Leffograptis, but in any case it is a new and undescribed form of the family. If it actually belong to Azygograptus, this is the first specimen of the genus on the American side of the Atlantic, and there is special appropriateness in its dedication to Mr. Walcott, whose recent researches have done so much to elucidate the sequence and fossils of the strata in which it occurs.
LEPTOGRAPTUS LAPWORTH, 1873. Geol. Mag. London, X, p. 558. Type, Z. flaccidus (Hall). Leptograptus ? macrotheca Gurley, sp. nov.
Known only in the form of a fragment of a branch. Thecz long, curved, slender, finally becoming nearly perpendicular to the branch but slightly
70 R. R. GURLEY
inclined distalwards; apertural margin straight ; proximal margin concave, not uniformly, but with a bluntly rounded angle. Thecz 16-17 in 25™™. Branch including theczee 1™™ wide, of which the coenosarcal canal occupies about two-sevenths.
Horizon and locality.—Calciferous shales, Point Levis, Canada.
DICELLOGRAPSUS HOPKINSON, 1871. Geol. Mag., VIII., p. 20. Type, D. elegans (Carruthers).
Dicellograpsus intortus* polythecatus Gurley, var nov.
A species occurs at Stockport which presents a close resemblance to Lap- worth’s species but shows some important differences, at least from his pub- lished description and figures. These differences are sufficient to justify its provisional varietal separation, although it is possible that they may be due to the structure being more perfectly shown by the Stockport specimens. It resembles Lapworth’s species, in the mode of growth, character of thecee and dimensions of the branches. Like that species the present form is alsoa Norman’s Kill (=Glenkiln) form. The thecee are uniformly 32 in 25™™. The first six or eight bear spines almost as long as the thece. But the most important difference is that the mode of growth is exactly the same as that exemplified by Dicranograptus furcatus (Hall), that is to say, the thece are present alternately on the outer and inner margins of the branches, and the latter cross alternately over and under, showing a growth in opposite-turning spirals. Lapworth’s figures indeed not only do not show this feature but on the contrary show the opposite condition. Nevertheless the conformity of type is so close that I suspect that this omission is an error, and that the British form, as well as the American, has the spiral mode of growth.
Where the proximal portion of the polypary is absent the appearance may resemble somewhat that of Dicranograptus furcatus (Hall) under similar con- ditions. The latter species has, however, much thicker branches (1™™ as against 0.6™™ for the present form), the thecae are much coarser and are a// provided with strong spines. The loops are also more elongate and narrow.
Horizon and locality._Lower Diécellograpsus zone, Stockport, N. Y. Dicellograpsus gurleyt Lapworth, sp. nov.
Branches from 25™™ to roo™™ long, slender, gently concave distally; diverg- ing immediately from sicula at an angle of 270°, which slowly decreases to a general angle of 240°; width at origin about 0.5"; maximum diameter 1.25™™ in adult parts of polypary. Thecz averaging about 24 to 26 in 25™™. without overlap, compressed proximally to form a deep excavation ; ventral margin straight for first three-fourths of its length; convex in last fourth, Distal portion of theca of the rounded type found in the genus, isolated and
t Dicellograpsus intortus Lapworth, was described in Ann. and Mag. Nat. Hist. 1880, V., p. 161, Plate XIX., Figs. 19 a-c.
NORTH AMERICAN GRAPTOLITES 7%
introverted, opening well within ventral margin of the polypary, the free portions occupying about one-fifth of entire length of theca. Excavation dis- tinct, deeply curved, occupying about one-third of transverse diameter of polypary, the interspaces taking up less than one-fifth of the ventral margin.
This form certainly belongs to a group of Dicellograpsi comprising besides it three species as yet undescribed. All these forms agree in having thece of the same general type, with very short, isolated distal portion and small introver- sion; but they differ in size, length, and angle of divergence of the branches, and in the proportion of their thecee. They are, however, all of the same geological age, and it is not outside the limits of possibility that they may be: local representative forms of one and the same species.
The whole group is intimately related to the group typified by D. forch- hammer? (Geinitz), into which it passes by almost insensible gradations.
Horizon and locality.—Lower Dzcellograpsus zone, Stockport, N. Y.
Dicellograpsus elegans (Carr).
Specimens occur in our Lower Dicellograpsus zone which agree in every respect with Carruther’s species except that they show 24 to 28 thece in 25™™,. while Carruther’s and also Lapworth’s figures show but 20 to 22.
Horizon and locality.—Lower Dzcellograpsus zone, Stockport, N. Y.
DICRANOGRAPTUS HALi, 1865. Can. Org. Rem., Dec. II., p. 112. Type, D. vamosus (Hall).
Besides D. furcatus two types of this genus occur in American strata, viz., D. nicholsont ,Hopk., with a very short proximal portion bearing very few thecee (ad plurimum 8 or g) and LD. ramosus (Hall), with a much larger proxi- mal portion bearing nearly twice as many thecz (usually 15 or thereabouts).
Of VD. nicholsonz 5 (perhaps ultimately reducible to 4) fairly well marked varieties occur which present a gradation from the non-spinose var. arkansas- enszs with an angle of 135° to go° through D. nzcholsonz (angle 80° to 70°) to the smaller angled spinose forms w/ztianus and parvangulus and finally to var. diafason with converging branches.
D. vramosus presents 2 varieties, the typical form with a stout polypary, occurring in the Lower Dicellograpsus zone and a much more slender variety occurring in the Upper Dicellograpsus zone at Magog.
Dicranograptus furcatus (Hall).
This species presents a very peculiar structure. In the compressed state it consists of several elliptic loops. The thecz begin on the proximal, diprion- idian portion, and are continued on the ow¢er side of the Zower half of the first loop. At the middle of the loop they become scalariform and on its “per half occupy the zzzer margin of the branch. Traced upward, on to the next loop, they are seen to be (owing to the recurving of the branch toward the median
GD R. R. GURLEV
line) again on the over side, and the same phenomenon is repeated with each loop. Thus the theca are always on the ow/ey margin on the /ower, and on the zzer margin on the wpper half of each loop. Further between the two branches at their points of crossing a film of shale can frequently be seen, the branches lying in the shale at slightly different levels. Also the branches always cross alternately over and under. All this is easily and only explicable upon the supposition that the branches originally grew sfzva//y upward, each describ- ing an oppositely directed curve. Compression would then produce the suc- cessive ellipses with the thece directed alternately outward and inward. This mode of growth in a continual spiral seems, as far as I can judge from Lap- worth’s figures of the species, to be exhibited by his Décellograpsus caduceus and D. ztczac.
Relative to its generic affinities it has been referred to both Dicellograpsus and to Dicranograptus, Waving early noted the presence of the thecz on the concavity of the first curve and the specimens not being the best, I thought it possibly a Dicellograpsus of the caduceus type, in which the first loop was closed. Better specimens, however, seem to show conclusively that the branches are united as in Dicranograptus. This portion is very short and like several other species it presents in this respect an approximation to Dzced/o- grapsus.
Horizon and locality.—Lower Dicellograpsus zone (of which it is one of the most characteristic species) near Stockport, Columbia county, N. Y.
Dicranograptus nicholsont Hopkinson. GEO, Mire, WIM WSO} [Os B57 Plate OWI, Wise 3
This species occurs in the Utica under a form which Professor Lapworth informs me does not differ from the typical.
Dicranograptus nicholsont arkansasensis Gurley, 1892.
Dicranograptus arkansasensis, Ann. Rep. Geol. Surv. Ark., for 1890, III., Doo HUO—7/, IFES IDK. IPI Uy Bs Proximal portion 9™™ long ; branches diverging at an angle of go° to 130°, curving upward at a short distance from their origin so as to include a smaller angle; thecze 20 in the space of 25™"; non-spinose. Horizon and locality.— Lower Dicellograpsus zone, Arkansas.
Dicranograptus nicholsont whitianus (Miller), 1883.
Graptolithus (Climacograptus) ramulus White (preoc.), 1874, Prelim. Rep. Invt. Fossils, p. 13; 26., White, 1875, Rep. Wheeler Survey, IV., Part I., p. 62, Plate IV., Figs. 3a-e; Graptolithus whitianus Miller, 1883, Cat. Amer. Pal. Foss., 2d ed., p. 269; Decranograptus ramulus Herrman, 1886, Nyt Mag. f. Naturvidensk., XXIX.
This form differs from the typical D. zzcholsonz of the Utica in the smaller
NORTH AMERICAN GRAPTOLITES 73
angle (35° or 40° against 70° to 80° in the Utica specimens) and in the pres- ence of short, rigid spines on the thecze of the stem and on practically all those of the branches. In the latter features lies its chief difference from var. parvangulus Gurley. I should add that a careful examination of the type specimen shows the proximal portion to be longer than shown in White’s fig- ure, at least six thecee being visible.
Dicranograptus nicholsoni parvangulus Gurley. (D. nicholsoni Lapw., 1876, Armstrong, Young & Robertson’s Cat. West. Scot. Foss., pp. 6-9, Plate III., Fig. 79; 20., Lapw., 1877, Ann. Rep. and Proc. Belfast Nat. Field Club, I., p. 141, Plate VII., Fig. 2.) Dicranograptus nicholsont parvangulus Gurley, 1892. Ann. Rep. Geol. Surv. Ark. for 1890, III., p. 417.
In the Stockport collection several examples of this variety occur which permit of the following description: Proximal portion about 6™™ long; at base 1™", and immediately below bifurcation 1.5" wide ; with eight or nine thece, each with a short, sharp horizontal spine ; branches 1™™ wide, diverg- ing at an angle of 35° or 40° (or thereabouts), often bending very slightly towards one another immediately after the division, thus producing a slightly rounded, bulging appearance. Thecze forming bent tubes, as in D. 22cholsont proper; as nearly as possible 24 in 25™"; those on the proximal portion and the first few on the branches above the bifurcation spiniferous. On the branches not more than three spiniferous thecz were seen.
Horizon and locality.—Lower D¢cellograpsus zone, Stockport, N. Y., and in Arkansas ; Upper Dicellograpsus zone, Magog, Canada.
Professor Lapworth (letter, 1890) remarks the difference between this form and D. nicholsonz, saying that this, the Glenkiln (= Lower Dicellograpsus zone) form, has a smaller angle and spinose proximal thece. D. mchclsonz proper is not found below the Utica. This variety, on the contrary, ranges through both the Lower and the Upper Déce/lograpsus zones but apparently not into the Utica.
Since publishing this variety, I have noticed its extremely close resem- blance to D. whitéanus Miller. Indeed the latter form appears to differ from the present one only in having all of the thecze on the branches spinose. I might at this time unite the two forms were it not that var. w/z¢zanws rests upon a single specimen from a very far distant locality, and it is possible that fur- ther collections in Nevada may show the distinctive characters of w/z¢zanus to be sub-constant. Finally it may be noted that none of the eastern, or of the Arkansas specimens show any decided approximation to the condition found in whztianus.
Dicranograptus nicholsont diapason Gurley, var. nov.
Proximal portion with three minute spines at base; measuring from base
74 Lie Iito, (GHUIRILIS NE
to notch between branches five (sometimes as much as 6™™"), showing below the level of the notch, at most seven (usually six, sometimes five) thecze ; width of proximal portion 1.25 to 1.50"; branches, in the compressed condition, I to 1.25™" wide; diverging at an angle of 45° (sometimes slightly less) to 50°, with a very gentle inward curve which brings them into parallelism, or even approximates them still further. Thecz forming bent tubes with the tip introverted, 24 or 25 in 25™™"; some of them (probably all on basal portion ; material here uncertain) bearing an acute spine.
This variety is a well-marked one. In form the most characteristic speci- mens approach closely D. zéczac minimus Lapw., but our form is at least twice as large as Lapworth’s, and besides D. zéczac appears not to occur in our strata. From the characteristic calliper-shape as a basis, the variety shades into var. Parvangulus, which has the branches straighter and contin- ually divergent.
Horizon and locality.—Lower Décellograpsus zone, Stockport, N. Y.
CLIMACOGRAPTUS HALL, 1865. Gany Ore. Rem, Dec 2,p. 3. Uype G. dzcornzs (Hall): Climacograptus antiguus Lapworth sp. nov.
(Climacograptus antiguus, Geol. Mag., 1873, X, p. 134, momen nudum ,; C. celatus, Lapworth, 1876, in Armstrong, Young & Robertson's Cat. West. Scot. Foss., p. 6, Plate I., Fig. 56; 2b., Lapworth, 13877, Ann. Rep. and Proc. Belfast Nat. Field Club, I, Part IOW35 JDs HBO} Plate VI., Fig. 39; 26. Lapworth, 1886, Trans. Roy. Soc. Can. for 1886, V. Sect. IV, p. 178. Synonymy fide Lapworth, letter.)
This being the first publication of the synonymy which establishes the species, it is to be regarded as a new one dating from this publication.
Climacograptus caudatus Lapworth," 1876.
Climacograptus caudatus, in Armstrong, Young & Robertson’s Cat. West. Scot. Foss., p. 6, Plate II., Fig. 48; 2b., Lapworth, 1880, Ann. and
Miaige Nateblists, Wil p22. Polypary attaining, in one proximally (“distally”) incomplete specimen, a length (exclusive of prolonged virgula), of 80™™. Maximum breadth, attained at proximal (‘‘distal’’) extremity, 2.25™. Polypary increasing gradually in width, nearly the full width being attained by the middle of the polypary, so that the widening is less rapid from that point to the proximal (‘distal’) extremity, which latter is abruptly cut off. Distal (“ proximal ”’) extremity marked by extension of virgula. Lateral spines not seen (condi- tions of specimens unsatisfactory.) Virgula about 0.75™" wide, prolonged
« For remarks on the present form and C. cawdatus Jaticaulis see next page.
NORTH AMERICAN GRAPTOLITES 75
both proximally and distally for about 25" without very obvious decrease in size. Theca 16 to 20 in 25™™", appearing to form bent tubes.
Horizon and locality—Upper Dicellograpsus zone, Magog, Canada.
Climacograptus caudatus laticaulis Gurley, var. nov.
(Climacograptus caudatus Lapworth, 1877, Ann. Rep. and Proc. Belfast Nat. HieldiGlub; > Part lV, p. 136, Plate Vil, Fig. 34°)
Polypary reaching a length of 60™" or somewhat more; usually shorter ; maximum width attained at extreme proximal (‘distal’) extremity, usu- ally 3.5"™" or a little more. Outline of polypary obtriangular, continuously widening from the rather blunt, 1™" wide distal (‘‘ proximal’’) extremity to the abruptly truncated proximal (‘‘distal’”’) extremity. Distal (‘‘ proximal ’’) extremity marked by two rather small lateral spines and further by the pro- longed virgula. Virgula strap-like, prolonged both proximally and distally at least 25" without any evidence of termination. In the distal (‘‘ proximal”) direction, the diminution in size in the distance mentioned is apparent, while in the proximal (“‘distal’’) direction, it is very slight. The broad strap-like virgula forms a conspicuous ridge-like elevation along the median line, of one lateral face, appearing less distinct on the other. Thecz 22-26 in 25™™, apparently with the outer wall concave-indented below, and rectangular above. Excavation indenting polypary for about one-third of its width, not at right angles but inclined (on distal side, of course) about 75° to virgula. Young individuals (with a length much less than maximum for the species) have, nevertheless, attained nearly the maximum width.
Horizon and locality.—Upper Dicellograpsus zone, Magog, Canada.
I at first had a great deal of trouble with the preceding two forms. The first light on the subject was obtained by noticing that to my two forms cor- responded respectively the two figured at different times by Lapworth under the name of Climacograptus caudatus. That they are at least varietally dis- tinct there is no doubt. For Lapworth’s caudatus of 1876 (which of course remains the caudatus) is about 2™".75 (possibly 3™" ad maximu) wide, has only 18 thecze in 25™™, and a more attenuated polypary which enlarges much more slowly; while the caudatus of 1877 (var. Zaticaulis) is 3"™ wide (probably, judging from my specimens, ad minimum), and has 24-26 thece and a more widely obtriangular polypary. Further in var. /atécaulzs the virgula is very stout and strap-like, recalling that of Diflograpsis foliaceus. Correlated with these differences in theca-numbers and polypary width, is the different pro- portions of the ‘“‘denticles.” In cawdatus rhombic, with the ventral and apertural margins about equal, in var. Zaticaulis they are considerably wider than long. It is possible that the forms are entirely distinct, but the material consisting merely of flattened films is not satisfactory on this point.
76 R. R. GURLEY
Climacograptus oligotheca Gurley, sp. nov.
Polypary acutely isosceles-triangular, long and slender, widening very slowly; distal (‘‘proximal’’) extremity bearing two short lateral spines. Virgula stout, occupying about one-sixth width of polypary, greatly prolonged proximally and distally, the distal (‘‘ proximal’’) extension sometimes consist- ing merely of a short triangular process, sometimes of a virgular extension terminating in a vesicular dilatation, but generally forming a straight broadly filiform process which may be traced for some distance without evidence of termination. No vesicle or “disk” visible at end of proximal (‘distal’) prolongation. Length, 11°" or less; width about 2™". Ventral margins straight, interrupted by notches corresponding to the thecal mouths. Thecz 1A (© WA iia BE,
Horizon and locality.—Upper Dicellograpsus zone, Magog, Canada.
This species is readily recognized by the proximal and distal extension of - the virgula, and by its straight parallel sides incised by a series of straight notches at comparatively distant intervals. It is most closely allied to C. antiguus, but is usually longer and has but 12 to 14 thece in 25™™", while C. antiguus has (by measurement on Lapworth’s figure) 20 in the same space.
Climacograptus caelatus Lapworth, 1875.
Quart. Jour. Geol. Soc. London, XXXI., p. 655, Plate XXXV., Fig. 8; not 2b., Lapworth, 1876 (see C. andiguus).
The principal interest in our specimens attaches to the ‘“‘disk’’ which forms the proximal (‘distal’) termination of the virgula. This body is an obtrian- gulat-cordate leaflet, bilaterally symmetrical, and traversed medianly by the virgula. Some appearances suggest that it may possibly consist of two super- posed elliptic leaflets. It is sometimes at a distance from, sometimes close to, or in actual contact with the proximal (‘‘distal”’) end of the polypary. From the (apparent) dilatations of the virgula seen in LD. veszculosus Nich., D. palmeus (Barr.), and D. trifidus Gurley, it differs markedly in its distinct bilateral symmetry, and flat leaf-like appearance. This “disk” is present in a large proportion of the specimens.
Horizon and locality.—Upper Calciferous, Summit, Nevada. Identified by Professor Lapworth from specimens sent him.
Climacograptus kamptotheca Gurley, sp. nov.
Polypary pretty uniformly 1™.5 broad and 35 to 4o™™ long; distally (‘‘ proximally”) tapering gradually for about length of last 7 or 8 thece to the narrow rounded extremity; maintaining its full width to the proximal (“distal”) extremity which is abruptly truncated. Virgula straight or slightly zigzagged, prolonged distally (‘proximally’) as a straight needle- like process, 2 or 3™ long; and proximally (“distally”) as a filiform exten- sion which in one specimen extends 12™™ without terminating in any “disk.”
NORTH AMERICAN GRAPTOLITES Wil
Thecz cylindrical, at first directed perpendicularly outward from virgula, then deflected through nearly 90° so as to become directed proximally (“distally”) and almost parallel with virgula, and at the same time to make a small angle with the plane of the shale-section (rising up from or sinking down into the rock); pretty uniformly 24 to 26 in 25™"; apparently without any overlap.
Horizon and locality.—Upper Dicellograpsus zone, Magog, Canada.
Easily recognized, in connection with the dimensions, by the superficial outline which shows a series of rather squarish thecal outlines distinctly alter- nating on the two sides.
Climacograptus phyllophorus Gurley, sp. nov. Plate IV., Figs. 4-6.
(Cliimacograptus parvus Hall, 1865, Can. Org. Rem., Dec.2, p. 57; nomen nudum.)
Polypary gradually widening from distal (‘‘ proximal’’) extremity, attaining its full width in the length of 6 to 8 thece; ventral margins above this point parallel. Length, exclusive of proximally (“distally”) prolonged virgula, 10 to 30™™ (usually about 20™); maximum width, 1™.5 to 2™™; distal (“proximal”) extremity narrow and abrupt, with two short lateral spines; and an extension of virgula for 2 to6™". Proximal (“distal”) extremity abrupt, showing a prolongation of the virgula which terminates in a “disk,” varying in shape (apparently with age) from narrowly lanceolate to broadly elliptic, 6 to ro™™ long, and 1 to 3™" broad. Thece 30 to 36 in 25™", short, perpen- dicular, apertural margins concave, the excavation nearly horizontal (slightly inclined distalward), occupying nearly one-third of width of the polypary.
Horizon and locality—Lower Dicellograpsus zone (of which it is one of the most characteristic species), Stockport, N. Y.
This species was identified by a comparison with Hall’s types in the American Museum of Natural History in New York City. It is very distinct from C. dzcornzs and C. tyficalis, differing from the former in the absence of the three prominent spines and the disk developed around them, and from the latter by the constantly prolonged virgula.* It is also much smaller than either dzcornzs or typicalts. The species which it most closely resembles is C. scalaris (L. =normatlis Lapworth), and for this form it has been mistaken (as it easily might be, and formerly was by me) by Ami.
The chief interest in the species lies in the “disk.” This has the form of and strikingly resembles an elliptic pinnate-veined leaflet, a resemblance heightened by the likeness of the virgula to the midrib, and the presence of several obscure, obliquely directed fibers running from it on either side out-
*If, as would naturally be expected, C. “ygzcalis has a proximally (“distally ”( extended virgula, it never (within my experience) shows it on the shale, and for prac- tical diagnosis this absence is all-sufficient.
78 I&s, £2) GUILE wards and proximalwards. An exactly similar but differently-shaped append- age is constant in C. caelatus from Nevada, and probably it is equally constant in C. phyllophorus, though here the longer, more slender virgula is more frequently broken. This appendage appears to differ from that found in such species as Diflograpsts vesiculosus Nich., in being accurately bilater- ally symmetrical, and in being plainly traversed by and not forming (as apparently is the case in D. vesiculosus) a dilatation of the virgula.
DIPLOGRAPSIS McCoy, 1850.
Ann. and Mag. Nat. Hist., VI., pp. 270-2. Type. D. Arestis Hisinger. Diplograpsis stenosus Gurley, sp. nov.
Polypary long and very slender, when complete probably measuring in the majority of cases about 50™”" or somewhat more; breadth 1 to 1.5™™, the latter figure being rarely exceeded. Polypary very gradually widening from near its distal (‘proximal’) end. Sicula and extreme distal (‘‘proximal”’) end of polypary unknown. Virgula usually obscure, frequently invisible, apparently not distally prolonged. Thecz about 20 in 25™”, straight, free for one-half of their length, inclined to virgula 25° to 30°; apertural margin probably perpendicular to virgula.
Horizon and locality.—Upper Décellograpsus zone, Magog, Canada.
No other species of the genus possesses a polypary so slender in propor- tion to its length. In this respect (only in this, however) it approaches most nearly some Upper Silurian species, notably D. zamariscus Nich., and D. longissimus Kurck.
GLOSSOGRAPSUS EMMONS, 1856. American Geology, I., Part II., p. 108. Type G. cz/zatus Emmons. Glossograpsus arthracanthus Gurley, sp. nov.
(Diplograpsus ciliatus Emmons, 1856, Am. Geol., I., Part II., pp. 1o5- Toon PlateweEcasros)
“Straight, thin and ciliated; cilia, bulbous and jointed or transversely marked, proceeding from the point of each serration; serrations unequal, the intervening smaller serrations rounded, the larger prolonged and run into the base of the ciliz, axis distinct.
“The specimen is imperfect, but probably, from the character of the column, it was free. The entire width of the column embracing the extended lateral ciliz is one-fourth of an inch, the membrane is rather less than one- eighth of an inch wide, the margins appear to be dissimilar. In another specimen the end is rounded and complete, and furnished like the sides with ciliz. Found in Augusta county, Virginia.”
This form is apparently a Glossograpsus. The name cz/zatuws having been previously used (by Emmons, and in the same paper) for a Glossograpsus, the name arthracanthus is proposed for this form to clear synonymy. The dupli-
NORTH AMERICAN GRAPTOLITES 79
cation of the “serrations” is probably due toa slightly oblique pressure causing the lower latero-ventral margin of the polypary to extend beyond the upper latero-ventral margin of the same, in such a manner that the corners of the thecal mouths alternate. I have seen this condition in G. cz/zatus and sev- eral other graptolite species.
LOMATOCERAS BRONN, 1834.
Lomatoceras, Lethzea Geognostica, I., pp. 55-56; MWonofrion Barrande, 1850, Grapt. de Bohéme, p. 14; JZonograpsus Geinitz, 1852, Die Graptolithen, p. 32; Monograptus of later writers; Lagenograptus Hall, 1870, 20th Rep. N. Y. St. Cab. Nat. Hist., 2 ed., p. 261. Type Z. Jriodon Bronn.
There can be no question as to the clear priority of this name, though it has been asserted, reasserted and taken for granted that it was preoccupied." I find no evidence of such preoccupation, at least I have searched with the aid of several entomological friends for the name as a genus of insects without success. Bronn says that his genus is “non Lomatocera, insectorum genus.” This is not preoccupation and there is no reason why both names should not stand. Finally if for any reason Lomatoceras cannot stand, Monograpsus must still give place to Barrande’s MJonofrion, as Geinitz’s alteration of the last to MWonograpsus (to harmonize with his substitution of Dzplograpsus for Diprion) preoccupied, cannot be accepted.
GLADIOLITE BARRANDE, 1850. Grapt. de Bohéme, p. 68. Syn. Refiolites, zbid., p. 68, footnote. Type G.
geinitzianus.
Barrande proposed G/adiolites as the name of the genus; merely adding that Refzolites could be used if (r/adio/ites were considered too near Gladiolus. By no rule of nomenclature can Aeézo/ztes have any standing (except as an unnecessary synonym). Accepted usage must therefore be rejected and Gladiolites restored.
Gladiolites venosus (Hall). EaloNe Venlo52; Ue pa40, blate x Villa, Migs. 22-4:
The figure of this species given by Spencer* and copied from him by Miller,3 bear no very evident resemblance to Hall’s species. Moreover, after a careful examination of a fine specimen (unquestionally co-specific with Spencer’s species) from the Niagara beds at Hamilton, Ontario (whence Spencer’s species came), has convinced me that the reference of it to G. venosus (Hall), is incorrect. Whatever else it may be it is not Hall’s form,
Beck in Murchison’s Silurian System, 1839, Part II., p. 696; Bronn, 1849, Geschichte der Natur, p. 667; Geinitz, 1852, Die Graptolithen, p. 18.
2Bull. Mus. Univ. State Mo., 1884, I., p. 16, Plate I., Fig. 2.
3 North Amer. Geol. & Pal., p. 202, Fig. 214.
80 I LR (GQUSSLIB M-
as, besides other reasons, it lacks any very evident graptolitic texture or struc- ture and has 24-26 oblique ribs as compared with (from measurements on Hall’s figures) some 35-40 for G. venosus.
RETEOGRAPTUS HALL, 1859. Pal. N. Y., IIl., p. 518. Type &. tentaculatus (Hall).
A specimen of &. ¢entaculatus in the American Museum of Natural His- tory, New York City, exhibits practically the same type of structure as is seen in PR. geznttzianus from the Lower Dicellograpsus zone. 1 have no doubt that they are congeneric. Lapworth has, however, referred PR. geznztzzanus to his Clathrograptus* (founded on C. cunetformis Lapw.). If C. cunetformis be, indeed, congeneric with &. gednztz¢anus, the genus Clathrograptus must be suppressed.
Reteograptus geinttzianus Hall, 1859.
Reteograptus geinitzianus, Pal. N. Y., Ill., p. 518, with fig.; Reteograptus barrandi Hall, 1860, 13th Rep. N. Y. St. Cab. Nat. Hist., pp. 61-62, with fig.; Clathrograptus geinitzianus Lapworth, 1880, Ann. and Mag. Nat. Hist., V., p. 22.
Some particularly favorable preservation-conditions occur among the Stockport specimens. They permit the following description: The polypary in this species is parallel-sided blunt-fusiform, and consists of skeleton and periderm. The skeleton shows, at and imbedded in its base a body appar- ently a sicula, flanked on either side by a spine which is directed obliquely upward. Two virgulas are present, each zigzagged in the basal expanding portion of the polypary, straight in the middle (parallel-sided) portion, and (?) again zigzagged in the upper contracting part. From the convex angles of the zigzagged, and at intervals from the straight portion of the virgula, a parietal ledge? runs in each lateral wall to the ventral margin, where it undergoes an abrupt deflection downward to the parietal ledge of the theca next below, to which it appears to connect just before (Zz. ¢., at a point on the lateral surface just within the ventral margin) that ledge reaches its point of downward deflection. At the latter point a mouth ledge connects the parietal ledge with its fellow on the opposite side. These three chitinous threads (the horizontal limb of the parietal ledge, the vertical limb of the same and the mouth ledge), all meet at the point of deflection with rounded edges, and together form the rim of the mouth opening, which is thus somewhat squarish or slightly trapezoidal. I have seen nothing corresponding to the inner cross-ledges and the material furnishes no data for an opinion pro or con as to the existence of any interthecal partition planes.
Geol. Mag., 1873, X., p. 559.
27 here follow the nomenclature of Holm (Bihang til kongl. Sv. Vet.-Akad.
Handl., 1890, XVI., No. 7).
NORTH AMERICAN GRAPTOLITES SI
The periderm consists of three, rarely only two,’ longitudinal series of meshes of a subrhomboidal shape which alternate in adjacent rows, and give off from the middle points of the meshes of the outer rows (the rows along the ventral margin) short, stout spines which are the mouth ledges crushed V-shape. The relation of the three rows of peridermal meshes to the skeleton is not known. ‘Uhe parietal ledges form the upper and lower bor- ders of the meshes, and are deflected inwards (7. ¢., into the intra-polyparial space) to their virgular connection at the inner borders of the outer rows of meshes (?), The meshes are covered by a membrane which is markedly thinner in the center of the mesh.
The structure is therefore in substantial agreement with that observed by Holm in Retiolites and Stomatograptus, the latter of which, Reteograptus,, seems particularly to resemble.
DICTYONEMA HALL, 1851. Am. Jour. Sci., XI., p. 4o1. Type D. retzforme (Hall).
Like Mr. Holm? I think the taxonomic condition in this genus very unsatis- factory. While there seems no possibility of denying to D. flabelliforme the possession of a true sicula, certain other species are certainly non-sicu- late. The extraordinary vertical range is also, as Mr. Holm remarks, good reason for suspicion of the generic references. When I first studied Des- mograptus macrodictyon, | thought Mr. Hopkinson’s genus was a first step in. the establishment of a natural series of cleavage planes in the genus, espe- cially as both species occur at equivalent horizons. But on subsequently studying D. devonicus | found that on no characters now predicated of Des-. mograptus could this species be denied admission to it. So that we only have two wide-ranging genera instead of one such genus. Another explanation. (one which has been suggested before, and one which, though I at first could not favor, I incline now to think not impossible) is that the characters (form,,. dimensions of mesh, thickness, etc. of branches) on which (being dependent on conditions of fossilization) we have to rely are really of very subordi- nate biologic value. And as Mr. Holm says there is no chance of a rational. subdivision until we know more of the basal end.
Dictyonema, cf. neenah Hall. Rep. Progr. Supt. Geol. Surv. Wisc., 1861, p. 7.
A single specimen, perhaps, referable to this species is found in the col- lection. It shows a considerable portion of the network, but not the proximal
*Several specimens show two series*below and three above, the interpolated middle series being wedge-shaped (7. e., narrower and less perfectly developed) below. The specimens showing the periderm are mzch larger than those showing the skele- ton, and though plainly congeneric, may not be cospecific.
? Bih. t. k. Svensk. Akad. Handl., 1890, XVI., Afd. IV., No. 7.
82 Teo Lk, (GIGUAGIE NC
extremity. The two layers of the flattened funnel-shaped polypary are pressed almost into contact, which circumstance, together with the slightly slicken-sided condition of the specimen, renders its accurate specific descrip- tion difficult. Enough, however, can be made out to state that, as flattened, the polypary is flabellate, 4o™™ in length, and the same in breath, of a tri- angular shape, with the distal side of the triangle rounded. The branches of the polypary are subparallel, very gradually diverging, about 1.5™™ apart, forking into two branches several times in their course towards the periphery.
Horizon and locality.
Upper Dicellograpsus zone, Magog, Canada.
1 have compared this form with the other species of the genus, and espe- cially with those forms which approach it in vertical distribution. Only two species have heretofore been described from approximately the same horizon, VizZ., D. moffatense Lapw., and JD. meenah Hall. With the former of these the present form needs no comparison. The latter species was described from the Trenton limestone of Wisconsin.
Dictyonema perexile Gurley, sp. nov. Dictyonema delicatulum Dawson, 1883, Can. Nat. and Quart. Jour. Sci. X.,
pp. 461-3; “D. n.sp. (=D. delicatulum Dawson, preoccupied)” Ami, 1889, Ann. Rep. Geol. Surv. Can. for 1887, p. 117 K.).
Proposed to replace Dawson’s delicatulum, that name having been pre- viously used by Lapworth (Quart. Jour. Geol. Soc., London, 1881, XXXVI, Os UY/2o))
Dictyonema actinotum Gurley, sp. nov.
Dictyonema hamiltonie Wall, 1865, Can. Org. Rem., Dec. 2, p. 58; nonien nudum.
Specimens seen very incomplete. Branches radiating rapidly, bifurcating mostly near the base (in correspondence with their rapid radiation) rather conspicuously longitudinal-striate, 0.5-0.6™™ wide, 25-30 in 25™™. Dissepi- ments rather stout, wiry, apt to be curved, transverse or slightly oblique. Meshes subquadrangular or with rounded angles. Thecz present but indis- tinct. Length of mesh uncertain, perhaps 2—2.5™.
Horizon and locality.—Devonian (Hamilton formation), Kashong Creek, Cayuga county, New York. Several specimens badly preserved, but apparently of this species, occur in the Hamilton at Moscow, N. Y.
Dictyonema blairt Gurley, sp. nov.
Proximal end of polypary unknown. Branches radiating slowly, sub- parallel, usually scarcely but nearly 0.4™™, occasionally 0.5™, ad max., and arranged transversely about 20-25 in25™™. Interspaces generally about one and one-half times as wide as branches or slightly more. Dissepiments rather slender, about 0.25", thick ad max. Sometimes straight. Usually more or less
NORTH AMERICAN GRAPTOLITES 83
oblique. Meshes correspondingly variable in shape, from quadrangular to triangular. The shortest are about 1.25™™" long, and the greatest length in unbroken meshes (¢. ¢., where all the dissepiments are entire) is probably near 3™". Texture Carbonaceous. Branches rather obscurely striate, dividing at an acute, rather sharp, angle.
Resembles somewhat 2. gvacz/e Hall, but the branches are a little more slender and the interspaces a little wider, and especially the number of branches transversely in this species is less (20-25 as against 25—30 in D. gracile), | am indebted to Mr. Charles Schuchert for having drawn my attention to this species.
Horizon and locality—Lower Carboniferous (Choteau limestone), Sedalia, Mo. Collected by and dedicated to Mr. R. A. Blair, of Sedalia.
DESMOGRAPTUS HOPKINSON, 1875.
Quar. Jour. Geol. Soc., London, XXXI1., p. 668. Type, D. cancellatum Hopk. Desmograptus macrodictyum Gurley, sp. nov.
Polypary subparallel, rather abruptly widening from a non-siculate, fibrous, root-like base; branches thick, almost straight, longitudinally striate, bifurcating quite regularly ; bifurcations evenly rounded, the dividing branches curving into parallelism and coalescing prior to redivision. Thecal mouths pressed against the stem, appearing as rounded or transversely oval eleva- tions, about 36 in 25™. Meshes very long in proportion to-their width, formed only by the coalescence of the branches, true dissepiments being entirely absent.
Horizon and locality.—Calciferous shales, Point Levis, Canada.
This species differs decidely from all species of Dzéctyomema except D. cancellatum Hopk., for which its author proposed (as a subgenus) Desmo- graptus, saying :
“The most distinctive characteristic is that the meshes or interspaces are chiefly formed by the branches coalescing and dividing by virtue of their curvilinear direction, being connected by transverse filaments only here and there where not sufficiently undulated to be brought quite into contact, and not being connected at all where the undulations do not bring the branches into tolerably close proximity to each other.”’
In the species here described no dissepiments are anywhere visible, the division of branches appearing to take place mostly at regular intervals, a series of divisions extending across the whole width of the polypary at the same level. I regard Desmograptus as entitled to full generic rank if, as I think, D macrodictyum belongs to it.
From all species it is distinguished by the entire absence of dissepiments ; from D. cancel/latum in particular by the straight branches, the greatly elon- gated meshes and the generally stouter structure.
84 R. R. GURLEY
Desmograptus devonicus Gurley, sp. nov.
(Dictyonema cadens Hall, 1865, Can. Org. Rem., Dec. 2, Pp. 58; momen nudum).
Polypary very irregular in its mode of growth; scarcely a true dissepi- ment present. Branches dividing and re-fusing irregularly, leaving round- elliptic or round-quadrangular (the prevailing type) meshes. The irregularity renders an accurate count of the branches difficult, but there seem to be about 12-15 in 25™™". The thickness varies considerably, though most of the branches measure 1™™”, or nearly that. Longitudinally, there are about six or seven meshes in 25™™,
Horizon and locality.—Devonian (Hamilton formation), Moscow, N. Y.
DENDROGRAPTUS HALL, 1862. Rep. Geol, Surv., Wisc., I., p. 21. Type, D. hallzanus (Prout).
Dendrograptus unilateralis Gurley, sp. nov.
Portion of polypary seen, 35™ in length, by 12™" in breadth. Branches in the single specimen seen, diverging mostly (entirely?) to one side, whence results a one-sided appearance; varying in thickness from 0.25™™ to 0.50™™, mostly approaching the latter size; given off at rather distant intervals, at a variable angle (roughly approximating 60°), very soon curving toward or into parallelism with the parent stem. Theca unknown.
The specimen consists of a slightly weathered, flattened film. Obscure indications of thecaze were seen, but they were too obscure to permit’ of detailed description.
Horizon and locality.—Upper Dicellograpsus zone, Magog, Canada.
Dendrograptus arundinaceus (Hall), 1847." Graptolithus arundinaceus, Pal. N. Y., I., Plate LX XIV. Fig. 8.
No description of this species has been published. Hall’s figure gives as much information as would a description of the same specimen, which, of course, is a mere fragment. I was able, however, to make out the distinctness from it of the Dendrograpti subsequently published.
Horizon and locality.—The type specimen (the only one) in the American. Museum of Natural History, New York City, was collected from the Utica shale, at Turin, Lewis county, N. Y.
Dendograptus, cf. serpens Hopkinson. Quart. Jour. Geol. Soc., London, XX XI1., 1875, p. 665, Plate XX XVII, Fig. 3
A single specimen referable to this genus in the Summit, Nevada, collec- tion seems most nearly related to Hopkinson’s species. It consists of an
t Overlooked entirely by cataloguers, which is not surprising considering its entire absence from both text and index.
NORTH AMERICAN GRAPTOLITES 85
exceedingly tangled maze of branches, most of which are of extreme tenuity, and cross and recross one another in inextricable confusion. A few larger branches are seen curving around and among the smaller. No thecz were observed, although certain indistinct crenulations may represent these struc- tures. Sicula and terminations, both proximal and distal, unknown.
Horizon and locality. —Upper Calciferous, Summit, Nevada.
CARYOCARIS SALTER, 1863. Quart. Jour. Geol. Soc., London, XIX., p. 139. Type, C. wrightzi.
This genus, referred by its author to the Crustacea, was defined as fol- lows:
“A long pod-shaped, bivalved carapace (with distinct hinge-pits), rounded anteriorly, subtruncate behind, and with the back and front subparallel. The surface is smooth, or with only oblique wrinkles near the margins, but with no parallel lines of structure. Body? Telson and appendages?
“All I know of this pretty little Crustacean, an inch long and rather more than a third of an inch wide, is contained in the above note. I was fortunate enough to find the tubercles (Huxley found them also in Ceratiocaris), which I suppose indicate teeth, and corresponding pits at each end of a short hinge-fulcrum.
“The shelly carapace is solid for its size; it appears to have a good deal of lime in its composition. The genus is evidently distinct, though so little is known of the entire form.
“ Everywhere in the Skiddaw Slate district. I have named it after Mr. Bryce M. Wright.”
It may be re-defined as follows: Polypary bilaterally symmetrical; proxi- mal portion possibly thecaphorous ; distal portion consisting of one (two?) median and two lateral appendages. Lateral appendages symmetrically disposed with reference to median line of polypary, apparently inserted on proximal portion through the medium of an elliptic body (“tubercles”’ of Salter); median appendage bilaterally symmetrical overlying superposed adjacent margins of lateral appendages. Texture yellowish-translucent, gauzy, resembling the wings of insects.
The above description is based upon American specimens of the type species, the other species being known only in the form of the lateral append- ages. The substance of the polypary does not differ much from that of the Diplograpses in the same beds. In texture it resembles Dawsonia more nearly than any other genus, and the resemblance is increased by the pres- ence of a marginal filament. At present, however, there is nothing to show that Dawsonia actually represents the lateral appendages of species of this genus, and the relationship of the two genera may be summed up as follows: The Dawsonias are certainly comparable, as regards texture and general appear-
86 I, Sie, (G OIILIE, SZ
ance to the lateral appendages found in Caryocaris, but to them only. Had these structures stood alone without evidence of further organization, I should probably have referred them to Dawsonza. But although a majority of these appendages are found isolated, in C. od/omgus all of the few specimens- obtained, and in the other two species, a not inconsiderable number of speci- mens are found paired in such a way as to leave no doubt that this is their normal condition, and their separation a result of decomposition. Further in several (of course very exceptional, but evidently so only as being exceptionally favorable preservation-conditions) specimens of C. wrighizz | have seen these symmetrically paired lateral appendages attached to the distal end of a single median proximal portion on which I believed thecz could perhaps be traced. It seems very doubtful indeed whether the future will show similar organiza- tion in any species at present referred to Dawsonia.
It is needless to add (as Professor Lapworth points out) that this is not, as Salter supposed, a Crustacean, but from its resemblance to Dawsonza appears to be a graptolite.
Caryocaris wrightit Salter, 1863. Plate V., Figs. 1, 2. Quart. Jour. Geol. Soc., London, XIX., p. 139, Fig. 15.
Polypary, consisting of a proximal portion, two lateral and one (two?) median appendages. Proximal portion acutely triangular, 9™™ long, 3™™ wide ad max. (at insertion of lateral appendages). Condition of thece uncertain. Lateral appendages round-triangular, obliquely truncated superi- orly by the superior margin, 7™™ long, 2.5 to 3™" wide ad max. (at point of divergence of adjacent margins), apex proximally directed, appareutly inserted upon the proximal portion through the medium of the “tubercle” which lies just within the outer margin; outer margin almost straight, bor- dered by a single filament which is interrupted by openings which appear to be continued into the substance of the appendage; superior margin slightly convex, running downward and inward, finally overlapping (or underlapping) the corresponding margin of the opposite appendage, furnished with a row of cilia-like processes ; inferior margins curving downward and outward around the “tubercle” to join the outer margin at the proximal extremity. Median appendage somewhat shorter than lateral, the superposed adjacent margins of which it overlies) acutely isosceles-triangular, symmetrical with reference to median line of polypary, the equal sides almost straight, the apex project- ing in the notch left by the diverging superior margins of the lateral append- ages.
Horizon and locality.
Upper Calciferous, Summit, Nevada.
The specimens occur only as flattened films, a condition unfavorable for the determination of structure. The symmetrical disposition of the lateral appendages would seem to imply a similar symmetrical structure in the
NORTH AMERICAN GRAPTOLITES 87
proximal portion of the polypary. Possibly a second median appendage may underlie (as the first overlies) the notch left by the diverging adjacent mar- gins of the lateral appendages.
This species is much less common than C. curvilatus. I have not as yet seen it in the Point Levis shales. The lateral appendages differ from those of C. curvidatus in their smaller size, triangular shape and in the single marginal filament, interrupted at intervals.
Caryocaris oblongus Gurley, sp. nov. Plate IV., Fig. 2.
Species known only in the form of the lateral appendages. These are roundish-oblong, about 15™" long and about 3” wide, showing near the proximal part a discolored spot which probably represents the ‘ tubercle.” Appendages superposed as in the other species of the genus. Substance thinner, presenting no evidence of structure. Filaments absent. No trace of median appendages.
Horizon and locality.—Calciferous shales, Point Levis, Canada.
This species is distinguished from the other two by its regularly oblong shape. There is no evidence that it represents a developmental stage of C. curvilatus.
Caryocarus curvilatus Gurley, sp. nov. Plate IV., Fig. 3; Plate V., Fig. 3.
Species known only in the form of the lateral appendages. These are broadly elliptic in outline, 20 to 30™™ long;
one margin convex, bordered by half a dozen horse-hair-like filaments which
Io™™ wide, more or less; with
run parallel converging toward the ends, enclosing a ribbon-like space which is obscurely transverse-striate (merely transverse-wrinkled ?); superior mar- gin with two acute processes between which extends a row of cilia-like pro- cesses; outer margin bordered by a single filament.
Horizon and locality. Point Levis, Canada.
This species presents very perplexing varieties of facies from differences in the amount and direction of pressure, and perhaps differences of age. Thus the width may be only one-third the natural, greatly altering the appear- ance of the species. But most difficult to decipher are the complicated foldings and refoldings of the marginal filaments; usually, however, these retain their parallelism. This latter fact implies that they were united by a thin membrane. The frequent foldings, however, show that they were either free except at one end, or (more probably, perhaps) that the uniting material was so thin as to offer no resistance to flexion.
Although the number of specimens are very numerous (forming more than one-half of the whole number of graptolite specimens from Nevada), I have not seen one specimen possessing the proximal portion. Several have,
Upper Calciferous, Summit, Nevada; Calciferous,
88 Li, Like (GOIALIB C
however, been seen with the appendages overlapping, both in the Nevada and in the Point Levis specimens.
The lateral appendages of this species differ from those of C. wrightiz and C. oblongus in their much larger size, usually more rotund shape, and in the multiple marginal filaments.
DAWSONIA NICHOLSON, 1873. Ann. and Mag. Nat. Hist., XI., p.139. Type, D. acuminata Nich.
-Dawsonia monodon Gurley, sp. nov. Plate V., Fig. 4.
Polypary somewhat rhomboidal in outline; Io to 14™™ long, 3 to 5™™ wide ad max., apex drawn out to a tapering mucro; dentate margin gently ‘curving from apex to the blunter extremity, interrupted at junction of upper with middle third by a small acute tooth; non-dentate border obtusely -isosceles-triangular joined near its lower end by a groove that has run close beside and parallel to it; proximal extremity rounded.
Horizon and locality.—Calciferous shales, Point Levis, Canada.
Easily recognizable by the single tooth and its (for the genus) large size.
Dawsonia tridens Gurley, sp. nov. Plate V., Fig. 5.
Polypary elliptic in outline, 3 to 4™™ long and 1 to 1™™.5 wide, with the ‘sharper extremity drawn out to a point; one margin bearing three acute teeth whose upper borders curve inwards, indenting the polypary and termi- ~nating in a ‘‘pustule” ; opposite margin smooth, joined at a very acute angle, near its lower end, by a groove which has run downward close beside and -parallel to the margin. The blunt extremity rounded, grooved for a short distance. Substance corneous, thin. The denticles can be seen to extend tinto the polypary whenever a thin film of shale separates the adjacent margins “of successive teeth, and seem to indicate thece, but from the extreme tenuity «of the film it is not possible to determine this point definitely.
Horizon and locality.—Calciferous shales, Point Levis, Canada.
This species is marked off from all other by the tridentate margin. In outline and size it resembles most closely DY. acuminata Nich.
THAMNOGRAPTUS HALL, 1859. s Pal. N. Y., Ill., p. 519. Type, 7. tygus Hall. Lhamnograptus barrandi Hall. .Rastrites barrandiz* Hall, Pal. N. Y., Ill,, 1859, pp. 520-521, with Fig.; Thamnograplus barrandit Lapworth, 1886, Tran. Roy. Soc. (Cain, ioe MIO, Wey SSCs Woy fOs UWS. This is certainly, as Lapworth says, a Zhamnograptus. A single specimen ‘shows, scalariform-wise, the thecal mouth-openings. They occupy about
The name Rastrites barrandii was preoccupied by Harkness (Quart. Jour. Geol.
NORTH AMERICAN GRAPTOLITES 89
two-thirds the width of the stem and are in the proportion of 25 to25™™. The aspect of the stem seems to oppose the view that the thecze project as in other genera form a coenosarcal canal. They appear rather to have been excavated out of the substance of the branch.
PHYCOGRAPTUS GURLEY, gen. nov."
Polypary consisting of long, slender, flexuous stems, apparently simple, with an entire border and many-segmented contents. Each segment with a single, central pit, seemingly the mouth of a cell, the latter apparently exca- vated in the substance of the stem. Sicula and virgula unknown. When preserved the substance is carbonaceous. Type ?. drachymera.
This genus forms one of a group the relation of which to the more typical graptolites is at present somewhat dubious. They are all of a carbonaceous texture and some in addition show pits, apparently the mouth-openings of a cell of some kind, but there is at present no evidence that such cell is of the theca type found in the more typical graptolites.
Phycograptus brachymera Gurley sp. nov. Plate V., Fig. 6.
Greatest length observed, 175™"; width, 1™"; number of segment in 25™", about 18; each segment as long as, or little longer than wide (rarely one and one-half times as long); pit large.
Horizon and locality.—Lower Dizcellograpsus zone, Stockport, N. Y.
Phycograptus laevis (Hall).
Graptolithus laevis Hall, 1847, Pal. N.Y., 1., p. 274, Plate LXXIV., Fig. 7; probably not 2d. Siiss, 1851, Haidinger’s Wissensch. Abhandl., IV., p. Bry Plates, Big.
A careful examination of the type specimen shows that it is about 55™™ long,’ uniformly about o™".8 wide throughout. In one place a break occurs which, in the light of the other species, I incline to interpret as a segmenta- tion, especially as the adjacent ends appear smoothly cut. Obscure traces of a median virgula-like chitinous thread are visible at intervals; no pits could be made out with certainty. The specimen is a mere film much wrinkled.
In another specimen I was able, however, to make out distinctly all the essential Phycograptus characters, viz., segmentation, pits, marginal grooves ; and, in addition, what appeared to be traces of a central chitinous virgula- like thread.
Horizon and locality.—Utica shale, Turin, Lewis County, N. Y. Two specimens in American Museum of Natural History.
Soc., London, 1855, XI., p. 475). As, however, the species has already been referred to, and is not preoccupied in 7hamnograptus, there is no reason why it should not stand. ‘puKos, sea weed; ypadw, I write. 2“Specimen uncovered after the figure made” (note on label).
Pre Aea IEW Jour, Gaon, Vou, IW, INO, 1
i AN Ta. MLL OF oI fl ei
_———————ee eee
1
fot Vet Vat Ua)
PLATE V. JOUREGrOR., Vow. [Vee Nowa
USS SS SSS SSS S SSS SSS SSSSE SSG SSS = cess
92 R. R. GURLEY
DESCRIPTION OF FIGURES.
PLATE IV.
Fic. 1.—Tetragrapsus acanthonotus; nat. size, and (1a) X 2.
Fic. 2.—Caryocaris oblongus, X 2. Showing conjoined lateral appendages.
Fic. 3.—Caryocaris curvilatus, X 2. Showing conjoined lateral appendages.
Fic. 4.—Proximal “disk” of Climacograptus phyllophorus; narrow form, X 2.
Fic. 5.—Climacograptus phyllophorus, X 2. Showing “disk,” and distal exten- sion from it of the virgula terminating in the “ polypary.”
Fic. 6.—Chimacograplus phyllophorus, XX 2.
AGRE Vie
Fic. 1.—Caryocaris wrightit Salter, X 2. Showing proximal portion, one median and two lateral appendages,
Fic. 2.—Caryocaris wrightit, < 2. Showing the lateral appendages, with the interrupted external, and the ciliated superior borders.
Fic. 3.—Caryocaris curvilatus, nat. size. Showing the outline, marginal fila- ments and ciliated superior border.
Fic. 4.—Dawsonta monodon, X $.
Fic. 5.—Dawsonia tridens, < 3. Showing the dentated border.
Fic. 6.—Phycograptus brachymera, X 6.
Fic. 7.—Didymograpsus bipunctatus, X 3. Fig. 7a, enlargement of thecz, X 6.
Fic. 8.—Didymograpsus convexus, X 3.
LIST OF GRAPTOLITES KNOWN FROM AMERICAN STRATA.
After some thought, I have concluded that I cannot do better than to connect this list with that given in our standard catalogue (Miller’s North American Geology and Paleontology ; and Supplement) as a base line. For this purpose the two lists (Miller’s and mine) are given in parallel columns. Italicized genera and species are new additions to Miller’s list, most of them, of course, being subsequent publications.
Acanthograptus Spencer, 1878. Acanthograpsus Spencer, 1878. granti Spencer, 1878. granti Spencer, 1878. pulcher Spencer, 1884. pulcher Spencer, 1884.
Amphigraptus Lapworth, 1873.* Type A. divergens. divergens (Hall), 1859. Azygograptus Nicholson, 1875. ? walcotti Lapworth, sp. nov. Bryograptus Lapworth, 1880. lentus Matthew, 1895.
NORTH AMERICAN GRAPTOLITES 93
Bythograptus Hall, 1861. laxus Hall, 1861.
Callograptus Hall, 1865. elegans Hall, 1865. granti Spencer, 1884. minutus Spencer, 1884, multicaulis Spencer, 1884. niagarensis Spencer, 1878. salteri Hall, 1865.
Calyptograptus Spencer, 1878. cyathiformis Spencer, 1878. [Omitted entirely. | [Omitted entirely. ]
subretiformis Spencer, 1878.
Cladograpsus Geinitz, 1852.
dissimilaris Emmons, 1856. inequalis Emmons, 1856.
Climacograptus Hall, 1865. antennarius Hall, 1863-5.
bicornis Hall, 1847.
emmonsi Walcott, 1886.
[Bryograptus Lapworth—cont'd. | multtramosus Gurley, sp. nov. patens Matthew, 1893.° spinosus (Matthew), 1893.77
Buthograptus Hall, 1861. laxus Hall, 1861.
Callograptus Hall, 1865. elegans Hall, 1865. granti Spencer, 1884. minutus Spencer, 1884. multicaulis Spencer, 1884. niagarensis Spencer, 1878. salteri Hall, 1865.
Calyptograpsus Spencer, 1878. cyathiformis Spencer, 1878. micronematodes Spencer, 1884. radiatus Spencer, 1884. subretiformis Spencer, 1884.
Caryocaris Salter, 1863. curvilatus Gurley, sp. nov. oblongus Gurley, sp. nov. wright Salter, 1863.
[Never properly defined; should be
dropped. | Dicranograptus dissimilaris. Dicranograptus ? inequalis.
Clathrograptus Lapworth, 1873. cuneiformis Lapworth, 1873.
Clematograptus Hopkinson, 1875,?
Type C. multifasciatus. multifasciatus (Hall), 1859.
Climacograptus Hall, 1865. Cryptograptus antennarius. antiguus Lapworth, sp. nov. bicornis (Hall), 1847.
peltifer Lapworth, 1876.3 tridentatus Lapworth, 1876.3 caelatus Lapworth, 1875. caudatus Lapworth, 1876. laticaulis Gurley, var. nov. confertus Lapworth, 1875. ? ?emmonsi Walcott, 1886.
94 R. R. GURLEY
[Climacograptus Hall—con?'d.] parvus Hall, 1865 [not defined]. typicalis Hall, 1865.
Clonograptus Hall, 1873. flexilis Hall, 1858. rigidus Hall. 1858.
Coenograptus Hall, 1868. Type C. divergens. divergens Hall, 1859. gracilis Hall, 1847. surcularis Hall, 1868. Cyclograptus Spencer, 1884. rotadentatus Spencer, 1884. Dawsonia Nicholson, 1873. acuminata Nicholson, 1873. campanulata Nicholson, 1873.
rotunda Nicholson, 1873. tenuistriata Nicholson, 1873.
Dendrograptus Hall, 1865. [Omitted entirely. | compactus Walcott, 1879. dawsoni Spencer, 1884. diffusus Hall, 1865. divergens Hall, 1865, dubius Miller, sp. nov. erectus Hall, 1865. flexuosus Hall, 1865. frondosus Spencer, 1884. fruticosus Hall, 1865. gracilis Hall, 1865.
[Climacograptus Hall—con?'d. | oligotheca Gurley, sp. nov. phyllophorus Gurley, sp. nov. scharenberg? Lapworth, 18763 typicalis Hall, 1865. qwilsont Lapworth, 1876.3
Dichograpsus Salter, 1863. Dichograpsus flexilis. Dichograpsus rigidus.
Corynoides Nicholson, 1867.4 Type
C. calicularis. calicularts Nicholson, 1867.4 Cryptograptus Lapworth, 1880.5 Type C. tricornis (=marcidus Hall). antennarius (Hall), 1865. tricornis (Carruthers), 1858.5 Stephanograptus Geinitz, 1866. Type S. gracilis. Amphigraptus divergens. Stephanograptus gracilis. Stephanograptus surcularis.
Cyclograptus Spencer, 1884. rotadentatus, Spencer, 1884.
Dawsonia Nicholson, 1873. acuminata Nicholson, 1873. campanulata Nicholson, 1873. monodon Gurley, sp. nov. rotunda Nicholson, 1873. tenuistriata Nicholson, 1873. tridens Gurley, sp. nov.
Dendrograptus Hall, 1862. arunadinaceus (Hall), 1847.° compactus Walcott, 1879. dawsoni Spencer, 1884. diffusus Hall, 1865.