MAMMALS. 



413 



Sub-Order 3. Pinnipedia. 



Aquatic petitadactyl carnivores, with webbed feet fitted for swimming, 

 incisors always less than §, p typically ^, m \, no differentiated carnassial ; 

 tail very short. 



The seals and their allies are mostly marine, although some ascend 

 rivers, while one species occurs in Lake Baikal. The body is fitted for an 

 aquatic life ; the basal portion of the fore limbs is imbedded in the general 

 integument, while the web of the toes usually extends beyond the extremity 

 of the clawed digits. The seals are true carnivores, feeding upon fish, of 

 which they destroy large numbers. The origin of the group is uncertain. 

 The eared seals show considerable resemblances to the ursidse, while the true 



Fig. 377. Harbor seals, Phoca vitulina, after Elliott. 



seals suggest an origin from some form like Lutra. So it may be that the 

 group is polyphyletic, or again, the pinnipeds may have descended directly 

 from the creodonts. The group first appears with forms allied to Phoca in 

 the miocene, while walrus-like forms occur in the pliocene. 



The OtariiD/E or eared seals have a small external ear, and the soles of 

 the feet naked ; teeth i \, c \, p |, m \ or \. Otaria includes sea-lions 

 of the Pacific and South Atlantic ; and the fur seals, most familiarly known 

 from the northern Pacific. The Trichechid.e, or walruses, have the ears 

 without external pinnae, and the upper incisors developed into immense 

 tusks. The species of Trichechus, one or two in number, are confined to the 

 northern parts of both oceans. The Phocid^ lack external ears, have the 

 soles of the feet hairy, the testes abdominal, the teeth p \, m \, and 



