XIII PHYLUM CHORDATA 497 



the fourth and fifth nearly equal. The tail is well developed and 

 prehensile. A number of Phalangers (Flying Phalangers) are 

 provided with lateral folds of skin extending from the fore- to the 

 hind-limbs and, acting as a parachute, enabling the animal, as in 



Fig. 1112. — Koala (Phascolarctos cinereus). (After Vogt and Spccht.) 



the Flying Squirrels, to perform flying leaps from tree to tree. 

 The Koalas (Fig. 1112) differ from the Phalangers mainly in the 

 relatively thicker body and the vestigial tail. 



The" Sloths (Bradypodidce, Fig. 1113) are more completely 

 adapted, in the structure of their litnbs, to an arboreal life than 

 any other group of the Mammalia. They have a short, rounded 

 head, with small pinnse, and long, slender limbs, the anterior much 

 longer than the posterior, with the digits, which are never more 

 than three in number, long, curved, and hook-like, adapted for 

 enabling the animal to hang and climb, body downwards, among 

 the branches of trees. In the three-toed Sloth there are three 

 toes in both manus and pes ; in the two-toed Sloth there are only 

 two in the manus, three in the pes. The tail is rudimentary. 

 The body is covered with long, coarse hairs, which differ from those 

 of other Mammals in being longitudinally fluted. On these hairs 

 grows abundantly an alga, the presence of which gives a greenish 

 tinge to the fur. 



The ordinary Anteaters {Myrmecophagidm) have a greatly elong- 

 ated snout, with the mouth as a small aperture at its extremity, 

 small eyes, and the auditory pinna sometimes small, sometimes well 

 developed. There are five digits in the fore-foot, of which the 

 third has always a very large, curved and pointed claw, render- 



