NATURAL SCIENCES OF PHILADELPHIA. 219 



Prof. Cope made some remarks on the Geology of Wyoming, 

 especially vvitli reference to the age of the coal series of Bitter 

 Creek. He said that the discovery of the Dinosaur Agathaumas 

 sylvestris had settled the question of age, concerning which there 

 had been much difference of opinion, in favor of the view that they 

 constitute an upper member of the Cretaceous series. In the 

 sections made, he had succeeded in tracing the line of demarcation 

 between these and the lower beds of the Green River epoch, and 

 had found the leaf beds of the former to be immediately covered 

 by deposits of mammalian remains, with an interval of a few feet 

 only. In the same way, the close approximation of the Evanston 

 cretaceous coal to tertiary strata was determined by the finding 

 of numerous mammalian and reptilian remains in the lower part 

 of the Wahsatch beds of Hayden, or even in the sandstones over- 

 lying the coal. Here two species of Bathmodon were found, cor- 

 responding with the nearly allied genus Melalophodon from the 

 Bitter Creek locality. So far as is yet known, the Balhmodontidas 

 are diagnostic of the Green River formation, and, on this and 

 other grounds, the Wahsatch beds of Evanston were regarded 

 as belonging to it. A further extension of the Green River 

 formation was found at a point 400 miles westward (see Proc. Am. 

 Philos. Soc, July, 1872), near Elko, Nevada, where fishes and 

 insects occur in thin shales. Some of the former are nearly allied 

 to species from the fish beds of Green River. 



He added that exception had been taken to his claiming the final 

 determination of the cretaceous age of the Bitter Creek coal strata 

 (see Silliman's Journal, 1872, Dec, p. 489); his critics presuming 

 that he was unacquainted with previous publications on the subject. 

 It was, however, his knowledge that previous authors had ex- 

 pressed either adverse or doubtful opinions respecting it, that 

 induced him to print the short preliminary notes that had appeared. 

 He was well aware that Messrs. King and Emmons had considered 

 the lower part of these beds as cretaceous, and the upper as 

 tertiary (see Exploration 40th Parallel, III. p. 458), on strati- 

 graphic grounds. Since the cretaceous was represented in different 

 parts of the country by clays, sands, giauconite, chalk, limestone, 

 and sandstone, he thought that palaeontological evidence was 

 needed to complete the demonstration. This had not been pro- 

 duced for the locality in question, but the nearest point (Hallville) 

 had been called Tertiary by Mr. Meek, and Prof. Lesquereaux 

 (Hayden's Survey of Terrs., 1870, p. 306) had considered the 

 fossil flora of Point of Rocks, forty miles westward, as of "unknown 

 age," and those of Evanston as miocene. Hayden himself is well 

 known to regard the strata as of uncertain or transitional age. 

 Paheontological determinations of cretaceous age of the Bitter 

 Oeek series were very indefinite up to the publication in question. 

 But first he would remark, that his critic was doubtless uninformed 

 as to the geography of Wyoming, when he cited Prof. Marsh's 

 determination of the cretaceous age of the coal of Brush Creek, a 



