190 YERTEBRATSS. 



CHAPTER VII. 



DIVISION I, -VERTEBRATES. 



CLASS I. — MAMMALS. 

 ORDER IV. ANIMALS OP THE WHALE TRIBE. 



The Cetacea, or animals of the Whale tribe, are distin- 

 guished by having no posterior extremities, and their anterior so 

 constructed as to answer the purposes of fins. In this order are 

 included whales, porpoises, dolphins, and narwhals, the grampus, 

 manati, and dugong. 



The whales are usually confounded with the class of fishes, 

 which they resemble in many particulars of external appearance, 

 as well as in the circumstance of residing always in the water. In 

 point of structure, however, they clearly belong to the class Mam- 

 malia, since they breathe air by means of lungs, are warm-blooded, 

 produce their young alive, and nourish them with their own milk. 

 Instead of fore feet, they are furnished with fins or oars, which, 

 however, are supported by bones similar to those of the fore feet 

 of quadrupeds. They have no hind feet, but their body terminates 

 in a thick tail, which supports a fin or oar. This fin is horizontal, 

 whilst that of fishes is vertical. 



A few of the Cetacea are herbivorous, and are fre([uently 

 obliged to leave the water and crawl upon the shore in search of 

 food. Such are the manati, usually called the sea-ox and sea-cow, 

 and the dugong. They have upon their fins the rudiments of 

 claws, which are of service to them in their motions upon the 

 land, and with which they are even able to carry their young. 

 The mammae, from which they nurse their young, are upon the 

 chest, like those of the human species ; and they have, around the 

 face, a growth of hair which resembles, in a slight degree, that 

 of man. Hence the appearance they present when the upper part 



