10 TAL^EONTOLOGY. 



The Cretaceous fo.ssils of tlic collection, as will be seen by plates 13, 

 14, and 15, are all merely casts of bivalves, excepting two species of Gas- 

 teropoda. Exclusive of the two species of large Inoceramus, represented 

 by fig. 3 of plate 13, and fig. 4 of plate 14, which came from a different 

 horizon near the eastern base of the Rocky Mountains, they are all from a 

 light-yellowish sandstone, containing beds and seams of brown coal, at 

 various localities in the region of Coalville and Bear River, Utah. The 

 specimens yet obtained are in a bad state of preservation ; but, as far as 

 can be determined, they appear to be very nearly if not quite all distinct 

 from the Cretaceous species yet known from the Upper Missouri country. 



Taken collectively, this group of fossils presents much the general 

 fades of the fauna of the series in California, referred by Professor Whit- 

 ney to the upper part of the Cretaceous of that State, under the name 

 Tejon Group. Yet, after careful comparisons with the figures and descrij)- 

 tions in the California reports, I am not fully satisfied that any of the 

 species are positively the sanic ; though in some instances they may at least 

 safely be regarded as closely-allied representative forms. "With the excep- 

 tion of the two or three species of Inoceramus, the genus Gyrodcs, and per- 

 haps Anclmra, they present, so i\ir as their characters can be made out from 

 the specimens yet brought in, just such a group of forms as might be, with 

 almost equal propriety, referred either to the Cretaceous or to the Tertiary.* 

 The presence of the genera mentioned, however, would, in the present state 

 of palajontological science, exclude them from the Tertiary and place them 

 in the Cretaceous. The fact, too, that they are all marine types, wliile all 

 of those yet collected in this great internal region of the continent, from 

 well-defined Tertiary Ijeds, are terrestrial, or fresh- and brackish-w^ater 

 types, woidd confirm the oilier evidence that these light-colored coal- 

 bearing sandstones of the region of Coalville and Bear River really belong 

 to the Cretaceous. Indeed, I arrived at this conclusion in 1860, while 

 investigating Colonel Simpson's collections from this formation.f The fact, 

 however, that all the collections yet brought in from this formation contain 



* Since this wiis written, Dr. Iliiyden's party have also brought in, from these 

 Coalville beds, other decidedly Cretaceous 'types of fossils. 

 tSee Proceed. Acad. Nat. Sci. Phiind., Ap. ISOO, p. 120. 



