442 GEOLOGICAL SUEVEY OF THE TERRITORIES. 



placement with faulting, which might very possibly cause the appearance 

 of the same beds both here and at the coal-mines, although at first sight 

 these would appear much higher in geological position. * * * I do 

 not know the grounds of Professor Cope's reference of the coal at this 

 point to the Cretaceous, while he admits the Tertiary age at least of 

 some of the overlying sandstones ; but as we found no break nor line 

 of demarkation in the whole 2,000 feet or more which we examined, and 

 found our fossils in coal-bearing beds immediately above and conform- 

 able to the main coal, the facts, so far as they are known to me, do not 

 seem sufficient for such identification."* This point offers, therefore, 

 a more complete continuity in stratification and mineral character from 

 the Cretaceous to Tertiary deposits than any other which I have had the 

 opportunity of examining. 



CONCLUSION.t 



Having traced the transition-series of the coal-bearing formations 

 of the Rocky Mountain region from the lowest marine to the highest 

 fresh-water epochs, it remains to indicate conclusions. I have alluded 

 but cursorily to the opinions of Mr. Lesquereux and Dr. Newberry as 

 based upon the study of the extinct flora. They have, as is well known, 

 pronounced this whole series of formations as of Tertiary age, and some 

 of the b'ids to be as high as Miocene. The material on which this de- 

 termination is based is abundant, and the latter must be accepted as de- 

 monstrated beyond all doubt. I regard the evidence derived from the 

 mollusks in the lower beds and the vertebrates in the higher as equally 

 conclusive that the beds are of Cretaceous age. There is, then, no alter- 

 native but to accept the result that a Tertiary flora teas contemporaneous 

 with a Cretaceous fauna^\ establishing an uninterrupted succession of life 

 across what is generally regarded as one of the greatest breaks in geo- 

 logic time. The appearance of mammalia and sudden disappearance of 

 the large Mesozoic types of reptiles may be regarded as evidence of 

 migration, and not of creation. It is to be remembered that the smaller 

 types of lizards and tortoises continue, like the crocodiles, from Meso- 

 zoic to Tertiary time without extraordinary modification of structure. 

 It is the Dinosauria which disappeared from the land, driven out or 

 killed by the more active and intelligent mammal. Herbivorous reptiles 

 like Agathaumas and Cionodon would have little chance of successful 

 competition v\ ith beasts like the well-armed Bathmodon and Metalophodon. 

 There is good reason for believing that this incursion of mammalia 

 came from the south. 



It then appears that the transition-series of Hayden is such not only 

 in name but in fact, and that paleontology confirms, in a highly satis- 

 factory manner, his conclusion, " already shown many times, that there 

 is no real physical break in the deposition of the sediments between the 

 well-marked Cretaceous and Tertiary groups." § 



* Hayden's Annual Report, 1872, p. 541. 



+ See Bulletin U. S. Geol. Survey Terrs., No. 2, p. 16. 



t The circumstance of the discovery of a mesozoic dinosaur, Agathaumas sylvestria, 

 ■with the cavities of and between his bones stuffed full of leaves of Eocene plants, 

 (Lesquereux,) would prove this proposition to be true, had no other fossils of either 

 kind ever been discovered elsewhere. 



§ Annual report, 1870, p. 166. For instance, Geol. Surv. Colorado, 1869, p. 197, Dr. 

 Hayden observes, " There is no proof, so far as I have observed in all the Western 

 country, of true non-conformity between the Cretaceous and Lower Tertiary beds, and 

 no evidence of any change in sediments or any catastrophe sufficient to account for the 

 sudden and apparently complete destruction .of organic life at the close of the Creta- 

 ceous period." 



