CLASS MAMMALIA 



657 



modified for life in the water. The hands and feet are fully 

 webbed, and serve as swimming organs, and the body has ac- 

 quired a fish-like form suitable for progress through the water. 

 They are chiefly marine, but a few inhabit fresh water, or swim 

 up rivers. The three families are the eared seals (Otakiid^e), 

 the walruses (OdobjEnid^e) , and the earless seals (Phoctd.e); 

 all of them have representatives on American shores. 



The family Otariid^e includes the sea-lions, fur seals, and sea- 

 bears. The fur seal, Otoes alascanus, breeds on tht Pribilof 

 Islands in Bering Sea, but at other times occurs along the coast 

 of California. Fur seals are polygamous, and a single old male 

 maintains control over from six to thirty females. One young 

 is produced each year. The three-year-old males, called 

 " bachelors," are the ones 

 killed for their fur. The 

 California sea-lion, Zal- 

 ophus calif ornianus, is the 

 member of this family most 

 often seen in captivity. 

 Squids, shell-fish, and crabs 

 are its principal articles of 

 food. Its fur is short, 

 coarse, and valueless. 



The family Odob^nid^: 

 contains two living species, 

 the Atlantic v/airus, Odo- 



bmnns rosmarus (Fig. 521), and the Pacific walrus, 0. obesus. 

 An adult male walrus is ten or twelve feet long and weighs 

 almost a ton. The canine teeth of the upper jaw are very 

 long, and are used to dig up mollusks and crustaceans from the 

 muddy bottoms, and to climb up on the blocks of ice in the 

 Arctic seas, where it lives. Walruses have been almost exter- 

 minated for their ivory, skins, and oil. 



The seals belong to the family Phocid^e. The harbor seal, 

 Phoca vitulina, inhabits the North Atlantic; the ringed seal, 

 2 u 



Fig. 521. — The walrus, Odoboenus ros- 

 marus. (From Flower and Lydekker.) 



