CLASS MAMMALIA 



415 



beavers; it is very rich in species, these numbering about one-third of 

 all of the species of mammals. 



Edentata (edenta'ta; L., edentatus, rendered toothless) includes 

 the highly modified and decidedly archaic sloths, armadillos, and ant 

 bears. They are found mostly in South America, although some species 

 occur as far north as Texas. Ants form a large part of their diet. In 

 spite of the name Edentata, ant bears alone are toothless; the others 

 possess teeth, but these lack enamel and are absent in the front part 

 of the jaws. The sloths are interesting because they are distinctly 

 arboreal animals, having a habit of hanging from the underside of 

 branches and following them in this position in locomotion. The arma- 



A B C D 



Fig. 285. — Bones of the foot in even- and odd-toed ungulates. A, pig; B, deer; C, 

 ox; D, horse. (From Schmeil, "Text-book of Zoology," by the courtesy of A. and C. Black, 

 and of Quelle and Meyer.) 



dillos (Fig. 284) have a well-developed dermal skeleton consisting of bony 

 plates covered with horny scales in which hairs are embedded. When 

 danger threatens, the animal curls itself up in its shell and thus protects 

 itself. 



443. Primates. — The lemurs, monkeys, apes, and man are primates. 

 Of these the lemurs are the most primitive and least manlike, having 

 many resemblances to the clawed mammals. In appearance they seem 

 to be intermediate between squirrels and monkeys. They are found 

 mostly in Madagascar but also in Africa and the Malay Archipelago. 

 The monkeys are divided into two types. The New World monkeys 

 are distinguished by a broad nasal septum, a small nonopposable thumb, 

 and a long prehensile tail, which is used like a fifth hand. The Old 

 World monkeys, on the other hand, have a narrow nasal septum with 



