CHAPTER IX 



THE RISE OF THE MAMMALS 



The rule of reptiles came to an end in the 

 Cretaceous, and witli the Eocene the mammals 

 assumed the supremacy; the name Eocene, dawn 

 of the recent, being given to this period of time 

 because it marks the beginning of the present 

 order of things. Mammals, as we have seen, 

 existed at the time of the dinosaurs, but were 

 then both scarce and small, as they apparently 

 still were during the Cretaceous period. That 

 they now appear in North America in numbers, 

 and include species of considerable size, means 

 that this is another of the cases Avhere links in 

 the chain of life are missing. They must have 

 been developing during the Cretaceous in some 

 locality yet unknown to us, or so many diverse 

 forms would not be found in the lower rocks of 

 the system. Thus at the very outset we find 

 representatives of several orders and not far 



220 



