152 ZOOLOGY. 



The essential points in which cetaceans differ from 

 quadrupeds, may be thus briefly enumerated : an ab- 

 sence of cylindrical and hollow bones a rudimental 

 and anchylosed state of the bones of the neck a 

 modification of the anterior extremities and tail, by 

 which these members are adapted to the office of fins 

 deficiency in posterior extremities and perfect pelvis 

 inability to respire through the mouth, or utter vocal 

 sounds copulation more humano and, probably, a 

 higher standard of animal heat. 



Cetaceans are naturally divided into three distinct 

 tribes, or families. The first of these is composed of 

 whales which feed on the vegetable productions of the 

 sea or rivers, and which are provided with teeth adapted 

 to the nature of their food. They may be regarded as 

 representing the herbivorous class of quadrupeds. They 

 include in their number, the Lamantins and Dugongs. 

 These whales do not blow or spout. 



The second family is formed by spouting-whales, of 

 predatory habits. They subsist chiefly on fish and 

 sepise ; have teeth adapted only for the prehension, or 

 coarse division, of their food ; and may be said to 

 represent the carnivorous quadrupeds of the land. 

 They are exemplified in the Cachalots, Porpoises, and 

 Dolphins. 



The third division comprises the Whalebone Whales, 

 as the Rorquals and Mysticetes (true or right Whales). 

 In the place of teeth, their jaws are provided with plates 

 and filaments of whalebone, (baleen,} which are moveable, 

 extensile, and adapted to retain, as in a net, the medusae, 

 or small marine animals which form the only food of this 

 colossal family. In habits they will bear comparison 

 with the insectivorous class of terrestrial quadrupeds. 



