41 



without extraordinar}- modification of structure. It is the Dinosauria which 

 disappeared from tiic laud, driven out or killed In- the more active and intel- 

 ligent mammal. Herbivorous reptiles like Agathaumas and Cionodon would 

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

 Bathinodon and Metalophodon. 



It then appears that the Transition series of Ha}'den is such not only iu 

 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 Annual Keport 1870, p. ICC. Also Geol. Survey Colorado, 18C9, p. 197, Dr. Hayden observes: 

 " There is no proof, so far as I have observed, in .ill the western country of true non-conformity between 

 the Cretaceous and Lower Tertiary beds, and no evidence of any cliange 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 



