ORDERS OF MAMMALIA. 



327 



As regards the geographical distribution of the Edentata, it is 

 to be remembered that the order has a, very limited range at the 

 present day. The true Ant-eaters, the Armadillos, and the Sloths, 

 are exclusively confined to South America, in which country a 

 group of gigantic extinct Edentates existed in the later portion of 

 the Tertiary epoch. The Scaly Ant-eaters are common to Asia and 

 Africa ; and the Ground Hog is confined to South Africa. 



Order IV. Sirenia. 



This order comprises only certain large marine Mammals, known 

 as Dugongs and Manatees, which were long classed with the Whales 

 and Dolphins {Cetacea). They agree with the Whales in the adap- 

 tation of the body to an aquatic life, especially in the facts that the 

 anterior limbs are converted into swimming-paddles (figs. 2.33, 234), 

 the hind-limbs are wholly wanting, and the hinder end of the body 



Fig. 233.— A, Side-view of young Manatm Avierieanus. B, the same viewe 

 from above ; n Nostrils. (After Murie.) 



forms a powerful caudal fin, which is placed so as to strike the 

 water horizontally, and not vertically as in Fishes. They differ 

 from the Cetacea in having the nostrils placed at the anterior part 

 of the head, and in having molar teeth with flat crowns, adapted for 

 a vegetable diet. Fleshy lips are present, the upper one usually 

 with a moustache, and the skin is covered with scanty bristles. 

 The head is not disproportionately large as compared with the 



