648 



CHORD AT A. 



the milk dentition degenerates early, without being functional. PHOCID.E. 

 seals, without external ears ; Phoca vitulina,* harbor seal. OTARIID^E, 

 with external ears ; Otaria,* sea lions ; Callorhinus ursinus, fur seal of 

 Alaska. TRICHECHID^E ; incisors reduced, upper canines developed into 

 large tusks ; Trichechus, walrus. 



The first carnivores appear in the eocene in the order CREODONTA, 

 plantigrade forms with slightly differentiated dentition (no carnassial) ; 



FIG. 670. Phoca vitulina, harbor seal. (After Elliott.) 



they present marked resemblances to marsupials, insectivores, as well as to 

 the Condylarthra, the ancestral ungulates. True carnivores appear in 

 the upper eocene and become abundant in the miocene. 



Order XI. Prosimiae. 



Linne united with the true apes a small group of animals 

 known as lemurs (from India and the adjacent islands, and 

 especially from Africa), because of similarity in body form and 

 climbing habits, because they had grasping hands and feet (oppos- 

 able thumb and great toe), and at least frequently nails on some 

 of the toes. To-day many set them aside as a separate order on 

 account of their lower organization. They have a less-developed 

 cerebrum, uterus bicornis, and a diffuse placenta. Further 

 peculiarities are the peculiar and variable dentition (Chiromys 

 }{)-if, Lemur f|||) and the presence of claws, which always occur 

 on the second and frequently on the third finger of the hind feet, 

 and in Chiromys replace the nails on all the digits of all the feet 

 except the great toe. Their nocturnal habits have resulted in 



