all other members of the kangaroo's order, in that mere cartilages represent those marsupial bones which every other member of the order unquestionably possesses.
Fig. 16.—Tasmanian Wolf (Thalacinus Cynocephalus).
The last family of the kangaroo's order consists of the true opossum, which (unlike all the animals we have as yet passed in review) inhabits not the Australian region, but America only.
These creatures vary in size from that of the cat to that of the rat.
They are called Dldelphidæ, and agree with the Dasyuridæ in having well-developed canine teeth and cutting back teeth (Fig. 17); in
Fig. 17.—Teeth of Opossum (Didelphys).
having the second and third toes free, and five toes to the fore-foot. But they differ in that
Cutting-teeth 10/8 (more than in any other animal).
A large opposable great-toe.
A tail, naked (like that of the rat) and prehensile.
One of them is aquatic in its habits and web-footed. Such are the very varied forms which compose the six families which together make up the kangaroo's order, and such are the relations borne by the kangaroo's family to the other families of the kangaroo's order.
But, to obtain a clear conception of the kangaroo, we must not rest content with a knowledge of its order considered by itself. But we must endeavor to learn the relation of its order to the other orders of that highest class of animals to which the kangaroo and we ourselves both belong, namely, the class Mammalia which class, with the
