216 THE CAMBRIAN. [bull. 81. 



Meek, the description of the fossils be found in the Black Hills during 

 the expedition of 1858. They* are Lingulepis pinnaformis, L. prima, 

 Obolella nana, and Agr aulas sp. 1 



A geueral description of the sandstone of the Black Hills is given by 

 Prof. K H. Winchell in his report to Capt. William Ludlow, and the 

 geographic distribution of the outcrop in the southern portion of the 

 Black Hills is shown on the accompanying map. 2 In the same report 

 Prof. K. P. Whitfield 3 describes Obolus pectenoides, a new species of 

 brachiopod, and also figures Lingulepis pinnafarmis. 



The report of Mr. Heury Xewton on the geology of the Black Hills 

 contains a detailed description and full discussion of the strata referred 

 to the Potsdam sandstone. This will be again referred to in the sum- 

 mary of our knowledge of the Cambrian rocks of the Black Hills. 4 From 

 the paleontologic portion of the report we learn that the entire fauna 

 of the Black Hills below the Carboniferous is Primordial, and Prof. R. 

 P. Whitfield states it closely resembles that from Wisconsin, and al- 

 though the species are nearly all distinct the generic facies is the same 

 throughout. 5 



In 1888 Prof. F. R. Carpenter published a series of notes on the geol- 

 ogy of the Black Hills, in which he criticised some of Newton's views, 

 and also advanced some theoretical considerations of interest in rela- 

 tion to the original deposition of the sediments forming the Potsdam 

 group. 6 



SOUTHWESTERN SUBPROVINCE. 



This includes the areas of Texas and Arizona. 



TEXAS. 



The presence of Silurian rocks in Texas, subsequently referred to the 

 Primordial, was announced by Dr. F. Roemer in 1849. 7 In the same 

 work he describes from the lower portion of the section Lingula acutan- 

 gula (p. 420) and Pterocephalia sanctisabce (p. 421). 



On the map accompanying this volume the entire Paleozoic series is 

 included under one color, on the northern side of the granitic band, 

 northwest of Austin. 



1 Paleontology of the Upper Missouri ; a report upon collections made principally by the expedition 

 under command of Lieut. G. K. Warren in 1855-'56. Invertebrates. Smithsonian Contributions No. 

 17-2.1864, pp. 2-10. 



2 Geological report of a reconnaissance of the Black Hllis of Dakota, made in the summer of 1874 by 

 Captain William Ludlow. Report of the Chief of Engineers, Appendix PP, 1876, p. 1170. 



3 Description of new fossils. Report of Geological Reconnaissance of Black Hills. A ppendix PP of 

 Report of Chief of Engineers, 1876, pp. 1202, 1203. 



4 Geology. Section IV. The Silurian. The Potsdam sandstone. U. S. Geog. and Geol. Surv. of the 

 Rocky Mountain region, J. W. Powell in charge ; report on the Black Hills of Dakota. 1880, pp. 

 80-107. 



* Paleontologj- of the Black Hills of Dakota. Report on the geology and resources of the Black Hills 

 of Dakota. 1880, pp. 329, 330. 



'Notes on the geology of the Black Hills. Preliminary Rept. Dakota School Mines on the Bkck 

 Hills of Dakota, 1888, pp. 11-52. 



7 Texas. Mit besonderer Riicksicht auf deutsche Auswanderuug und die physichen Verhiiltuisse 

 des Landes nach eigener Beobachtung geschildert. Bonn, 1849. 



