NATURAL SCIENCES OP PHILADELPHIA. 11 



the age of the latter as cretaceous, contrary to the opinion ex- 

 pressed by some geologists, that the formation both in Dakota and 

 Colorado is tertiary. 



Mr. Cope incidentally mentioned the recent discovery of remains 

 of Dinosaurs in the lignite beds of Colorado, which Avere thus proved 

 to belong to the cretaceous period, and not tertiary, as the evi- 

 dence of the fossil plants had been interpreted by Mr. Lesquereux 

 and others. 



Dr. LeConte expressed his great satisfaction at the complete 

 confirmation, by his friend Mr. Cope, of the statements he made 

 several 3^ears ago,* concerning the cretaceous age of the lignites at 

 the eastern base of the Rocky Mountains, from near Denver 

 southwards into New Mexico. Dr. LeConte had discussed the 

 subject on page 19, and more fully on Go and 66 of his report. 

 He had, it is true, expressed on page 65 a suspicion that the lig- 

 nites of the Missouri basin might be of miocene age, but it would 

 be seen by the narrative part of the report that Di\ LeConte had 

 not examined these beds personally, and their tertiary age was 

 assumed only in deference to the very strong!}' expressed opinion 

 of Dr. Hayden, "the pioneer and most successful explorer 

 of the Missouri basin" (Report, page 53), who was the first, 

 as he has been the most persistent advocate of this view. 

 While admitting the similarity of the flora of these lignites to 

 those of known tertiary localities, he had insisted on the greater 

 value of the stratigraphical and zoological evidence by which they 

 were shown to be cretaceous. He referred Mr. Cope to this report, 

 that he might see how perfectly these recent discoveries accorded 

 with the previously expressed views, which Mr. Cope had, perhaps 

 inadvertently, omitted to mention. 



Mr. Cope replied that he was quite familiar with the report of 

 Dr. LeConte, but did not consider stratigraphical evidence of 

 value as compared with palseontological in this instance, because 

 the beds display continuity of deposit from cretaceous to tertiary 

 (Hayden), while the fauna and flora exhibit an interruption. 



Prof. Frazer remarked that in this opinion Mr. Cope differed 

 from geologists generally, who regarded the weight of palaeonto- 

 logical evidence as based entirely on our previous knowledge of 

 stratigraphical relations, and where the field was so new as our 

 Western territories, the evidences of palaeontology as establishing 

 synchronism with the geological ages of Europe must be received 

 with great caution. 



' Notes ou the Geology of the Survey for the Extension of the Union 

 Pacific Railway, Eastern Division. Philadelphia, Feb. 1867. 



