MAMMALIA 359 



structure and habits; they are not genuine flyers but merely soarers 

 that parachute from tree to tree by means of folds of skin stretched 

 between the fore and hind limbs. The koala is a curious slow-moving, 

 nocturnal animal, that feeds almost exclusively on the leaves of the 

 gum tree. It has been called "marsupial bear," but is really more 

 like a large "Teddy Bear" than anything else, as the illustration 

 (Fig. 185, E) plainly attests. 



Family 9. Macropodidce {Kangaroos, Wallabies, etc.). — The kan- 

 garoos are mostly terrestrial forms, but some of them appear to be 

 secondarily arboreal. The hind legs are very large and powerful and 

 usually the fourth and fifth toes are much enlarged into a sort of hoof. 

 The tail is always long and heavy at the base. Macropus rufus (Fig. 

 185, A) is the largest of the marsupials, attaining a length of five and 

 a half feet, exclusive of the tail. They are very fleet of foot, progress- 

 ing by great leaps of the long hind legs covering twenty feet at a 

 jump. The fore legs are of no use in running and appear to be merely 

 for grasping food and for handling the young. The genus Petrogale 

 (Fig. 185, B) includes kangaroos that live among the rocks, using 

 the long tail as a balancing pole as they leap from rock to rock. 

 Dendrolagus (the tree kangaroo) is very different in its habits from 

 any of the other members of the family. The foot structure indicates 

 that the arboreal habit has been superimposed upon an ancestral 

 cursorial habit, for there is the same great enlargement of the fourth 

 and fifth toes as in the other kangaroos. 



Family 10. Phascolomyidce (Wombats). — This family consists of 

 but one genus, Phascolomys. It is in general appearance something 

 like a small bear (Fig. 185, G) or a heavily built marmot. It lives 

 entirely on the ground and moves about with a sort of shuffling 

 plantigrade gait much after the manner of a bear. It is shy and 

 gentle, though it can put up a vigorous defense with teeth and claws 

 if forced to do so. In habits it is nocturnal, spending the daytime 

 in burrows or holes among the rocks. 



