genera. 2. Dorcopysis, with a very large first back tooth. 3. The tree kangaroos (Dendrolagus), which frequent the more horizontal branches of trees, have the fore-limbs but little shorter than the hind-limbs, and inhabit New Guinea; 4. The rat-kangaroos (Hypsiprymnus) which have the first upper grinding-tooth large, compressed, and with vertical grooves.
Fig. 6.—Skull of a Rat-Kangaroo (Hypsiprymnus).
These four genera together constitute the kangaroo's family, the Macropodidæ, the species of which all inhabit Australia and the islands adjacent, but are found nowhere else in the world.
The species agree in having—
1. The second and third toes slender and united in a common fold of skin.
2. The hind-limbs longer than the fore-limbs.
3. No inner metatarsal bone.
4. All the toes of each fore-foot provided with claws.
5. Total number of incisors only 62
These five characters are common to the group, and do not co-exist in any other animals. They form, therefore, the distinguishing characters of the kangaroo's family. This family, Macropodidæ is one of the six other families which, together with it, make up that much larger group, the kangaroo's order. As was just said, to understand what a kangaroo is, we must know "what are the relations borne by his family to the other families of its order;" and accordingly it is needful for our purpose to take at least a cursory view of those other families.
There is a small animal, called a bandicoot (Fig. 7), which, in external appearance, differs very plainly from the kangaroo, but resembles it in having the hind-limbs longer than the fore-limbs, and also in the form of its hind-feet, which present a kangaroo structure, but not carried out to such an extreme degree as in the kangaroo, and therefore approximating more to the normal type of foot, there being a rudimentary inner toe and a less preponderant fourth toe; the second and third toes, however, are still very small, and bound together by skin down to the nails. In the fore-foot, on the contrary, there is a deficiency, the outer toes being nailless or wanting. The cutting-teeth are more numerous, these being I 108
This little creature is an example of others, forming the family
