320 MAMMALS 



It is a curious and interesting fact that the hoofed mam- 

 mals walk on the ends of their toes, which, however, are 

 incased in a horny covering called a hoof. The hoof is a 

 modification of the skin. 



Among the odd-toed mammals are the tapirs that live 

 in the tropical forest regions of both continents. They 

 resemble hogs in appearance and form, but have a large, 

 prehensile upper lip. 



The rhinoceroses, which have three toes on each foot, are 

 -found in Africa and Asia. They have a very thick skin 

 which, in some species, is thrown into folds. The snout 

 bears one or two horns quite different in structure and origin 

 from those of cattle. The Indian rhinoceros has one horn ; 

 while the black rhinoceros of Africa has two, one situated 

 in a line directly behind the other. The white rhinoceros 

 of Africa is a huge beast rivaled in size among the land 

 animals by the elephant only. 



The horse has only one toe, but the so-called " splint 

 bones " are the existing remnants of a second and a fourth 

 toe. In the western states a remarkable series of fossils 

 have been found showing the development of the horse 

 from forms about the size of a fox with three toes behind 

 and four toes in front. 



The even-toed group of hoofed mammals have as their 

 lowest representative the hippopotamus, of which there 

 ,are only two species, both found in Africa. They have 

 four toes, a huge, ungainly body, and large canine teeth 

 developed into tusks. They may be seen in large herds in 

 the rivers of Africa, in the daytime, apparently for the 

 simple pleasure of being in the water. They can remain 

 beneath the water for a considerable interval of time, and 

 to facilitate such a habit the nostrils can be closed by 



