AMERICAN GEOLOGY THE LARAMIE QUESTION. 649 



other long- list of genera characteristic of the Cretaceous certainly left 

 its molluscan fauna with strong Tertiary facies. When, however, he 

 came to consider these fossils in their specific relation he found that 

 all, with possibly two or three exceptions, were new to science and 

 quite different from those yet found either at Bear River or Coalville, 

 or, indeed, elsewhere in any of the established horizons. He felt, 

 therefore, that he could scarcely more than conjecture from their 

 specific affinities to known forms what the probable age of the rocks 

 might be in which they were found. He, however, called attention 

 to the following facts relative to the age of the formation as found at 

 Hitter Creek: 



First. That it was conformable to an extensive fresh-water Tertiary 

 formation above, from which it did not differ materially in lithological 

 characters except in its containing numerous beds of coal. 



Second. That it seemed also to be conformable to a somewhat 

 differently composed group of strata below, apparently containing 

 little, if any coal, and believed to be of Creta< eons age. 



Third. That it showed no essential difference of lithological char- 

 acters from the Cretaceous coal-bearing rocks at Bear River and 

 Coalville. 



Fourth. (Omitting references to Lesquereux's determinations) that 

 all its animal remains thus far known were specifically different from 

 any of those found in any other formation of this region, with possibly 

 two or three exceptions. 



Fifth. That all its known invertebrate remains were mollusks, con- 

 sisting of about thirteen species and varieties of marine, brackish, 

 and fresh-water types, none of which belonged to genera peculiar to 

 the Cretaceous or any older rocks, but all to such as are alike common 

 to the Cretaceous, Tertiary, and present epochs, with possibly one 

 exception. 



Sixth. That, on the other hand, two or three of its species belong- 

 to sections or subgenera apparently characteristic of the Eocene- 

 Tertiary of Europe, and even very closely allied to species of that age 

 found in the Paris basin, while one species seemed to be conspecific 

 with and two congeneric with forms found in brackish-water beds on 

 the upper Missouri containing vertebrate remains most nearly allied 

 to types hitherto deemed characteristic of the Cretaceous. 



Seventh. That one species of Anomia found in it is very similar to 

 and perhaps identical with a Texas Cretaceous shell, while a Viviparus, 

 found in one of the upper beds, is almost certainly identical with 

 the V. trochiformis of the fresh-water Lignite formations of the 

 upper Missouri, •( formation which has always been considered as 

 Tertiary. 



