No other known beast besides walks upon a single toe in each hind-foot, save the horse family (horses, asses, and zebras), and they walk upon a different one, namely, that which answers to our middle-toe, while Chæropus walks on the next outer one or fourth. No known beast besides Chæropus walks upon two toes in each foot, save hoofed creatures, such as the ruminants and their allies; but in them it is the third and fourth toes that are used, while in Chæropus it is the second and third toes.
Another animal, called a phalanger (of the genus Phalangista) is a type of a third family of the kangaroo's order, the Phalangistidæ, a family made up of creatures which live in trees and are nocturnal in their habits, feeding upon fruits and leaves. Here we find the limbs of nearly equal length. Once more we have I 6⁄2, and we still have the second and third toes united in a common fold of skin; but the inner-most toe (that answering to our great-toe) is not only largely developed, but is like that of the apes, directed outward, and capable of being opposed to the other toes, as our thumb can be opposed to our fingers.
Some of these creatures have prehensile tails. Others have the skin of the flanks enlarged so as to serve them as a parachute in their leaps, whence they are called "flying opossums," just as squirrels, similarly provided, are called "flying" squirrels.
There are two very aberrant members of this family. One, the koala. Fig. 9. (Phascolarctus), called the native bear or native sloth, is devoid of any tail.The other, Tarsipes, but little bigger than a mouse, has a long and