

3STO- lO. 



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

 with reference to the age of the coal series of Bitter Creek. He said that 

 the discovery of the Dinosaur Agatliaumas sylvestris had settled the ques- 

 tion of age, concerning which there had been much difference of opinion, 

 in favor of the view that they constitute an upper member of the Creta- 

 ceous series. In the sections made, he had succeeded in tracing the line 

 of demarkation 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. Iii 

 the same way, the close approximation of 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 overlying the coal. Here two species of 

 Batlimodon were found, corresponding with the nearly allied genus Meta- 

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

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

 and other grounds, the "Wahsatch beds of Evanston were regarded as be- 

 longing 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 deter- 

 mination of the cretaceous age of the Bitter Creek coal strata (see Silli- 

 man's Journal, 1872, Dec, p. 489) ; his critics presuming that he was un- 

 acquainted with previous publications on the subject. It was, however, 

 his knowledge that pi-evious authors had expressed either adverse or 

 doubtful opinions respecting it, that induced him to print the short pre- 

 liminary 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 

 stratigraphic grounds. Since the cretaceous was represented in different 

 parts of the country by clays, sands, glauconite, chalk, limestone, and 

 sandstone, he thought that palsenotological evidence was needed to com- 

 plete the demonstration. This had not been produced 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 west- 

 ward, as of "unknown age," and those of Evanston as miocene. Hay- 

 den himself is well known to regard the strata as of uncertain or transi- 

 tional age. Palsenotological determinations of cretaceous age of the Bitter 

 Creek 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 



