572 MAMMALS. 



Sub-class EuTHERiA — Order i. Edentata. 



This order includes five very distinct families with living 

 representatives — the sloths, the ant-eaters, the armadillos, 

 the pangolins, and the aard-varks. The first three families 

 are found in the New World, the last two in the Old "World. 

 So diverse are the five types that only one characteristic 

 can be stated : — the teeth are either absent or simple and 

 imperfect. When present they are uniform, and except in 

 Tatusia and Orycteropus there is only one set ; moreover, 

 they are without roots, and grow from persistent pulps, are 

 without enamel, and are never developed on the fore part 

 of the mouth. 



The modern Edentata are specialised survivors of a 

 waning order, whose extinct representatives seem to have 

 been larger and more primitive. The modern forms usually 

 have protective peculiarities of structure and habit which 

 secure their persistence. Thus some are arboreal, others are 

 burrowers, and many are covered with strong armature of 

 bone or of horn. It is interesting to observe how very varied 

 the nature of the placenta is : — 



a dome-shaped disc (deciduate) in the sloths, 



dome-shaped or discoidal (deciduate) in the ant-eaters, 



discoidal (deciduate) in the armadillos, 



diffuse (non-deciduate) in the pangolins, 



zonary (deciduate) in the aard-varks. 



Families of Edentata. 



J. Bradypodidje — Sloths. — The three-toed sloths (Brady pus) and the 



two-toed sloths {Cliolcepui) are restricted to the forests of South 



and Central America. They are the most arboreal of mammals, 



passing their whole life among the branches, to which they 



hang and along which they move back downwards. They are 



solitary, nocturnal, vegetarian animals, sluggish as their name 



suggests, and with a very firm grip of life. Their sha^y 



hides harmonise with the mosses and lichens on the branches, 



and the protective resemblance is increased by the presence 



of a green alga on the hair. Their food consists of leaves and 



shoots and fruits. 



The body is covered with coarse sh^gy hair ; the head is rounded 



and bears very small external ears ; the fore-limbs are longer than the 



hind-limbs, and the two or three digits are bound together by skin 



and have long claws ; the tail is rudimentary. 



