41 



without extraordinary modification of structure. It is the Dinosauria which 

 disappeared from the land, driven out or killed by the more active and intel r 

 ligent mammal. Herbivorous reptiles like Agathaumas and Cionodon would 

 have little chance of successful competition with beasts like the well-armed 

 Bathmodon and Metalophodon. 



It then appears that the Transition series of Hay den is such not only in 

 name but in fact, and that paleontology confirms in a highly satisfactory 

 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." 1 



1 Annual Report 1870, p. 16G. Also Geol. Survey 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 catastro- 

 phe sufficient to account for the sudden and apparently complete destruction of organic life at the close 

 of the Cretaceous period." 

 6 



