122 ELEMENTS Off COMPARATIVE ZOOLOGY. 



bears and otters in particular. As has been said, their feet 

 are modified into paddles, and only the distal region is dis- 

 tinct from the body. Lowest are the large walruses, of 

 which there are two species in northern seas, in which the 

 upper canines are enormously developed. They can use 

 their hind feet in walking. The eared seals are so-called 

 because they have small external ears. The largest of these 

 are the sea-lions, but the most valuable are the fur seals, of 



FIG. 52. The harbor seal (Phoca vitulina). After Elliott. 



which two species are known. The one which occurs in the 

 southern hemisphere has been almost exterminated, while 

 the Alaskan species is rapidly following the same road. 



The true seals lack all external ears, and since their skins 

 are less valuable, a longer lease of life seems assured them. 

 They occur on all shores, and from their fish-eating habits 

 are frequently a nuisance to fishermen. 



