xii PHYLUM CHORD ATA 525 



and third toes of the hind-foot slender and united by a web, 

 as in the Kangaroo, but the hallux, which is nailless, op- 

 posable to them ; and the fourth and fifth nearly equal : the 

 tail is well developed and prehensile. The Koalas (Fig. 294) 

 differ from the Phalangers mainly in the relatively thicker 

 body and the vestigial tail. 



FIG. 294. Koala (Phascolarctos dnereus). (After Vogt and Specht.) 



Of the Edentata, the Sloths (Bradypodida) (Fig. 295) are 

 more completely adapted, in the structure of their limbs, to an 

 arboreal life than any other group of the Mammalia. They 

 have a short, rounded head, with small pinnae and long 

 slender limbs, the anterior much longer than the posterior ; 

 the digits, which are never more than three in number, are 

 long, curved, and hook-like, adapted for enabling the animal 

 to hang and climb, body downwards, among the branches of 



