212 THE CAMBRIAN. (bull. 81. 



of the Yellowstone Lake region are represented as surrounded by the 

 same formation. 1 



At the South Pass of the Wind Biver Mountains Dr. Hayden found 

 the granites occupying a very restricted area and extending from them 

 a large thickness of M Potsdam" sandstone containing Obolella nana 

 and a Lingula. 2 



Prof. F. H. Bradley in 1873 identified the "Quebec group" by the 

 presence of Oonocoryphe and Dikelocephalus in limestones upon the 

 flanks of the Teton range of mountains. At one of the outcrops of 

 these limestones " they are immediately underlaid by about 300 feet of 

 partly compact, partly shaly, glauconitic sandstones, which are evi- 

 dently equivalent to the so-called Knox sandstones of Safford, which 

 form in Tennessee, the lower part of the Quebec group. No fossils 

 were seen in these beds. They are apparently unequally distributed, 

 since no corresponding beds appear along the caiion of West Teton 

 Creek. Beneath them, and often present when they are absent, we 

 generally find from 50 to 75 feet of a very compact ferruginous quartz- 

 ite which must represent the Potsdam, though this also, is sometimes 

 wanting." 3 In a diagram of a section extending from Henry's Fork 

 through the Teton Mountains the so-called Quebec group and Potsdam 

 quartzite are represented on each side of the range, the quartzite rest- 

 ing directly on the granite. 4 



The preliminary paleontological report of Mr. F. B. Meek refers the 

 beds containing fragments of Conocoryphe and Dikelocephalus, found 

 on the west base of Big Horn Mountains by the Hayden survey in 1872, 

 to the Potsdam or Primordial zone. 5 



In speaking of the Paleozoic rocks of the Laramie Hills, Mr. Arnold 

 Hague states that all paleontologic evidence obtained from these beds 

 would tend to show that they beloug to the Coal Measure limestone. 6 



The strata along the eastern slope of the Wind River Mount. lins re- 

 ferred to the Potsdam by Dr.Haydeu were studied by Prof. T. B. Coin- 

 stock while geologist of Capt. W. A. Jones's expedition to northwestern 

 Wyoming. He found the sandstone closely resembled that described 

 by Prof. J. D. Whitney in Wisconsin. The local peculiarities of this 

 sandstone and its associated rocks as described in the Mississippi Val- 

 ley and New York are strikingly repeated in the Pocky Mountain' 

 region. The greatest thickness of the sandstone in the region of the 



1 Geological report of the Exploration of the Yellowstone and Missouri Rivers. Under the direction 

 of Capt. W. F. Raynolds, 1859-'(30, Washington, 18G9, p. 144, map. 



2 Report of F. V. Hayden (on the geological survey of Wyoming.) U. S. Geol. Surv. of the Terr., 

 4th Ann. Rep., 1871, p. 33. 



3 Report of Frank H. Bradlej', goologist of the Snake River division. U. S. Geol. Surv. of the Terr., 

 6th Ann. Rep., 1873, p. 216. 



"Op. cit., p. 218. 



* Preliminary paleonfolegical report . . . with remarks on the ages of the rocks, etc. U. S. Geol. 

 Survey of the Territories, embracing portions of Montana. Idaho, Wyoming, and Utah ; 6th Ann. Rep. 

 1873, p. 431. 



6 Descriptive geology, U. S. Geol. Expl.of the Fortieth Pat.; Ciarence King, vol. 2, p. 76. Washing- 

 ton, 1877. 



