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EVOLUTION OF ANIMALS 



Part V 



Fig. 37.13. Walrus (Odobenus). An arctic marine carnivore with a massive body 

 of 2000 pounds or more, small head, ill-favored face and upper canine teeth grown 

 into tusks 2 feet long. Above the tusks its lazy gentle disposition is apparent. It is 

 the original model of the "walrus mustache." (Courtesy, American Museum of 

 Natural History, New York.) 



size, as much as three inches across the crown. Elephants eat large amounts 

 of herbage but do no after-meal chewing like cattle. 



Cetacea. Toothed whales, porpoises and dolphins, and whale-bone whales 

 are all typically marine. Some are gigantic, the largest living animals. All are 

 streamlined, fish-shaped. The skin is extremely thick, underlaid with fatty 

 blubber, and almost or entirely hairless in the adults, but hairy in the young. 



All of the toothed whales (Fig. 37.17), porpoises, and dolphins are car- 

 nivorous, having simple pointed teeth — numerous in some species, few in 

 others. Toothed whales are the killers; the males run in schools in the Atlantic 

 and Pacific oceans and far into the antarctic; the females are said to stay 

 in the tropics. Dolphins are small-toothed whales, five to 14 feet long; one of 

 them is the "killer whale," regarded as the most ferocious mammal in the sea. 



The whale-bone whales feed upon the minute plants and animals that live in 

 surface waters. The adults have no teeth. In place of them are plates of horn, 



