ART. 17 MOLLUSKS FEOM WYOMING EEESIDE AND WEYMOUTH 5 



Besides the molliisks, in the matrix of the specimens described 

 in this paper the fish scales LeucichthyoiJs vagans Cockerell ^° and 

 Erythrinolepis mowriensis Cockerell ^^ were noted. 



All of these species except some of the specimens of Metoicoceras 

 luhitei came from the NW. i^ sec. 32, T. 21 N., R. 115 W., at horizons 

 70 to 100 feet below the top of the formation, which is there 670 feet 

 thick. Some of the specimens of Metoicoceras tohitei Hyatt came 

 from sec. 17, T. 16 N., R. 117 W., at a horizon 350 feet below the top 

 of the formation, which is there 820 feet thick. 



The pelecypods help but little in the correlation of the fauna. 

 The ammonites, on the contrary, assist materially. Kanahiceras 

 occurs in the middle Eagle Ford shale of Texas, in the Greenhorn 

 limestone of eastern Colorado, in the lower part of the Colorado 

 group in southern Utah, and in the Mowry shale of southern 

 Wyoming, in all these in association with species of lower Turonian 

 age, such as Inoceramus labiatus. Ejpengonoceras occurs in the 

 middle part of the Eagle Ford shale of Texas and in the Mowry 

 shale of the Black Hills of eastern Wyoming, in both regions in 

 association with lower Turonian species ; and in somewhat older beds 

 elsewhere, as the upper Cenomanian of France. Metoicoceras is 

 widespread in America, chiefly in beds of lower Turonian age — 

 middle Eagle Ford shale. Greenhorn limestone, lower part of the 

 Mancos shale, Mowry shale, Mosby sandstone member of Warm 

 Creek shale, etc. — though in Texas it occurs also in somewhat older 

 beds (lower Eagle Ford or upper Woodbine),^- and in Europe is 

 said to range from upper Cenomanian to lower Turonian. The 

 species found in the Aspen shale is Turonian. Acompsoceras has 

 been reported from the Cenomanian of Europe and north Africa, 

 but not yet from the Turonian. The writes consider the Aspen 

 fauna to be of lower Turonian age and equivalent to that of the 

 lithologically similar Mowry shale, though it has some similarity to 

 that of the Greenhorn limestone, which in the Black Hills region 

 lies as much as 1,000 feet above the Mowry shale. The relations of 

 the Aspen shale to the lower part of the Colorado group at various 

 other places can be determined in only a general way — that is, it 

 is equivalent in age to a very early part. 



10 Cockerel], T. D. A., Some American Cretaceous flsh scales, with notes on the classifica- 

 tion and distribution of Cretaceous fishes : U. S. Geol. Survey, Prof. Paper 120, p. ISO, pi. 

 34, fig. 13; pi. 35, figs. 1-15, 1919. 



11 U. S. Geol. Survey, Prof. Paper 120, p. 182, pi. 36, figs. 3-6. 

 ^ Stephenson, L. W., unpublished data. 



