792 



GEOLOGY 



those of cats, and others those of seals. Some species seem to ha> 

 been aquatic. Primitive representatives of the dog family appear? 

 in Europe late in the period. 



Edentates, rodents, and insectivores. The similarity of the ai 

 cestral edentates to the condylarths and creodonts of the earlio 

 Eocene seems to imply that the three orders had but recently <1 

 verged from common ancestors. The primitive rodents of the ear 



Fig. 532. Mounted skeleton of Patriofelis, a Creodont from the Middle 

 Eocene of Wyoming; Ms natural size. (Osborn). 



Eocene had incisors which had just begun to assume their specific 

 gnawing functions. By the middle of the period, rodents became 

 a notable element in the fauna, the Tillothm'um- of the Brid^cr 

 formation having finely specialized incisors (Fig 533). The primi- 

 tive squirrel appeared in Europe in the latter part of the period. 

 Even to-day, the rodents retain many primitive character-, and 

 since the Miocene they have undergone few radical changes. Their 

 derivation is not yet determined. 



Most living families of insectivores can be traced back to the 

 Eocene. They still retain many primitive; characters, and are the 

 least altered of the great mammalian branches. 



