2 PROCEEDINGS OF THE NATIONAL MUSEUM vol.78 



station in T. 14 N., R. 118 W., Uinta County, on a part of the Union 

 Pacific Railroad, since abandoned in favor of a shorter route lying 

 some miles farther north. Veatch described the formation as " dark- 

 colored, splintery, somewhat arenaceous shales containing abundant 

 fish scales," and ascribed to it a thickness of 1,600 to 2,200 feet, with 

 the average at 1,800 feet. 



The beds comprised in the Aspen formation at the type locality 

 had been clearly noted, however, by most of the earlier students of 

 the region,^ the references extending at least as far back as 1870. 

 Stanton* in 1892 recorded near old Bear River City from "several 

 hundred feet of bluish and brownish shales," that are undoubtedly 

 part of the present Aspen shale, " teleost fish scales and crushed 

 specimens of a Prlonocyclus (perhaps P. woolgari) ." These ammonites 

 are now recognized as belonging to some species of Metoicoceras ^ 

 and agree therefore with the fauna described below. Schultz has in 

 several papers ° described the Aspen shale of the same general region. 

 He records it as composed of black shale, dark drab arenaceous shale 

 and gray sandstone, 1,200 to 1,800 feet thick but averaging 1,600 feet, 

 at places weathering into small splintery fragments and producing 

 long rounded hills of peculiar silver-gray color, and containing 

 abundant fish scales. In sec. 19, T. 24 N., R. 115 W., Lincoln County, 

 it yielded specimens of Lingula species. 



The most notable lithologic feature of the Aspen shale is the 

 presence of zones of a very hard, very fine-grained rock which 

 weathers to a platy, very light gray, resistant material and causes the 

 formation of conspicuous and very characteristic ridges along the 

 outcrop. Identical material constitutes most of the Mowry shale of 

 central and eastern Wyoming, recently studied by W. W. Rubey,^ 

 who concluded that its peculiarities are due to an unusual content of 

 silica, and that this was derived from the alteration of volcanic ash. 

 The fossils described in the present paper are all preserved in this 

 hard siliceous rock. Mr. Rubey has studied specimens of this matrix 

 and has very kindly rontributed the following note : 



The three samples from the Aspen formation are all very hard, light to 

 medium gray, fine-grained rocks. The sample reported as most representative 

 is somewhat coarser grained than the others and distinctly light gray, both on 

 the weathered surface and in fresh fracture. Its weathered surface is con- 



» For references see Veatch, footnote 2. 



* Stanton, T. W., The stratigraphic position of the Bear River formation : Amer. Journ. 

 Sci., ser. 3, vol. 43, p. 104, 1892. 



B Stanton, T. W., personal communication. 



« Schultz, A. R., Coal fields in a portion of central Uinta County, Wyo. : U. S. Geol. 

 Survey Bull. 316, p. 215, 1907 ; Geology and geography of a portion of Lincoln County, 

 Wyo. : U. S. Geol. Survey Bull. 543, pp. 30, 59, 1914 ; A geologic reconnaissance for phos- 

 phate and coal in southeastern Idaho and western Wyoming : U. S. Geol. Survey Bull. 680, 

 pp. 13, 28, 1918. 



' Rubey, W. W., Origin of the siliceous Mowry shale of the Black Hills region : U S. 

 Geol. Survey Prof. Paper 154, pp. 153-170, 1929. 



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