296 GENERAL ZOOLOGY 



recent geological times certain fossil elephants, like the 

 mastodon and mammoth, lived in the Northern Hemi- 

 sphere. 



Order 13. Sirenia. The manitees and dugongs are 

 large aquatic animals which live in shallow waters along 

 the sea shore and in the mouths of rivers. These great 

 animals live on vegetation and the bones are very heavy so 

 that they may remain on the bottom without effort. Their 

 limbs are modified to form flippers which, with the tail, 

 serve for swimming. 



Order 14. Cetacea. There are two kinds of whales: 

 (1) those with teeth (Odontoceti) ; and (2) those in which 

 the teeth are never functionally developed, being present 

 in the young but replaced by baleen or " whalebone" in the 

 adult (Mystacoceti). Though whales are fish-like in 

 general form and wholly aquatic in their habits, they are 

 true mammals. The body before birth has a thick coating 

 of hair, and the young are nourished with secretions from 

 the mammary glands. A whale's nostrils open through 

 the " bio whole" on the top of the head, and a great cloud 

 of spray and vapor is spouted from this aperture when it. 

 comes to the surface to breathe. The toothed whales in- 

 clude the dolphins, porpoises, grampuses, killer whales, 

 sperm whales, and narwals. The baleen whales are as a 

 rule of large size, including the great rorquals, fin-whales, 

 hump-backed, and right whales. " Whalebone" hangs 

 from the roof of a whale's mouth in long plates which are 

 frayed out at the free ends. In feeding, water is taken into 

 the mouth and squirted out between the plates, thus 

 straining out many small animals. The sulphur-bottom 

 whale, Balcenoptera sulfureus, is the largest living animal. 

 It may attain a length of ninety-five feet and weigh nearly 

 300,000 pounds. 



Probably the greatest interest which any man has in 

 mammals relates to his own relationships to animals in 

 general. The next two chapters will accordingly be devoted 

 to man as an animal and his place in the animal kingdom. 



