376 



LAND MAMMALS IN THE WESTERN HEMISPHERE 



derivative genera may continue to live side by side in the same 

 region. ]Promerycochcerus, it is believed, gave rise to \Mery- 

 cochoerus, but survived with it into the middle Miocene. 

 ^Merycochcerus, in its turn, produced ^Pronomotherium, and, 

 so far from being replaced by the latter, actually outlived it and 

 persisted into the lower Pliocene. 



A third phylum of the foreodonts, which appeared for the 

 last time in the middle Miocene (genus '\Cyclopidius), was a 



Fig. 199. — ^ Promerycochoerus carrikeri, lower Miocene. Restored from a skeleton in 

 the Carnegie Museum, Pittsburgh. 



series of small and very small species, of which the skull was 

 almost as peculiar as that of ]Pronomotherium, but in a dif- 

 ferent fashion. The face was very much shortened and on 

 each side a great vacuity reduced the nasal bones to mere 

 splints ; the elevated position of the eye-sockets, which pro- 

 jected above the forehead, and of the tubular entrance to the 

 ear is an evidence of an aquatic or amphibious mode of life, 

 such as is illustrated by the hippopotamuses, which can float 

 almost completely submerged, with only the ears, eyes and 



