KANGAROO-RAT.
These are also called Potoroos, and are of small size, being about that of a Hare or Rabbit. They have a compact body, the neck being short, and the ears are rather rounded, so that their shape is unlike that of the Great Kangaroo, but it resembles that of the smaller kinds somewhat. They have a rat-like shape, both hind feet like the Kangaroos, a long tail, and peculiar teeth. The head is very like that of a Rodent, and the incisor teeth in the upper jaw have the front ones the longest. The canine teeth exist in the upper jaw, and the premolar is large, and has numerous distinct vertical grooves on the outer and inner sides; and the front molars are the largest, the smallest being in the rear. The toes of the fore foot are unevenly developed; the three central ones are large, and those at the side are small. The nails are solid, broadest above, and much compressed. The foot is long, and the fourth toe and nail are greatly developed. The fifth toe is next in size, and the small second and third are coupled together by skin, and form a projection, with two small nails, which are useful in combing and scratching the fur. The first toe is absent. The Rufous Kangaroo-Rat inhabits New South Wales, and is very common.[94] Its nest is made up of grasses, and is frequently placed under the shelter of a fallen tree, or at the foot of some low shrub. During the day the little animal lies curled up in its nest, but it occasionally reposes in a “seat” like the Hare Kangaroo; but it never sits in the open plains. On being pursued it jumps like a Jerboa, with great swiftness for a short distance, and seeks shelter in hollow logs and holes. Its food consists of roots and grasses. Another is a native of Van Diemen’s Land, and keeps to the open, sandy, or stony forest land, rather than to the thick and humid bushes. It is called Hypsiprymnus cuniculus.
TEETH OF THE KANGAROO-RAT.
None of the animals hitherto described as Kangaroos have any prehensile power in the tail; but in one group of the Kangaroo-Rats, the tip of the tail has a brush of long hairs above, and is clothed beneath with short hairs, which are closely applied to the skin. This structure, and the motion of the muscles beneath, give the Tufted-tailed Kangaroo-Rat[95] of New South Wales a power of encircling and holding objects, especially for seizing grasses with which to make its nest. This is placed in a hollow in the ground, excavated for its reception, and its opening being on a level with the surrounding herbage, the practised eye of the native is required to discern it. After the little things creep in, they drag some grass after them, and close up the place. In the evening, they sally forth and scratch and dig up roots with their strong fore-claws.
THE RAT-TAILED HYPSIPRYMNUS.[96]
The Rat-tailed Kangaroo-Rat is about fifteen inches and a half long, and the tail measures, in addition, more than nine inches. It has a long head and rather short hind feet, and the rat-like tail has short stiff hairs on it which do not quite hide the scaly skin beneath. The body fur is long and loose, and dusky brown, more or less tinted with black and pale yellowish-brown. The end of the nose or muzzle is spotted, and the ears are short and rounded. This little animal lives in New South Wales, and was that which was first described by Hunter under the name of Potoroo, or Poto Roo, being the “Bettong” of the natives of New South Wales. The stomach of the Kangaroo-Rats is less sacculated than that of the Kangaroos, but its left-hand portion is enormously developed in proportion to the rest, and may be compared with that of the Ruminantia in point of relative size. It may be noticed that the lower jaws of the Potoroos, which are largely inflected at the angle, articulate with the skull rather differently to those of the Kangaroos. In these last, the cavity at the base of the zygomatic process which receives the lower jaw is broad and slightly convex, permitting considerable side-to-side movement which is useful in the occasional “cud chewing.” But in the others the cavity barely deserves the name, it being a nearly flat surface, and, therefore, not much motion, except that of an up-and-down kind, is possible to the jaw. The organ of hearing has been slightly noticed in the Great Kangaroo in a former page, and it is necessary to observe that the tympanic bone does not form a perfect tube in the Potoroos as in the Kangaroos, and that the surface of the auditory cavity is also increased by a “bulla,” or bony cavity, bulging out at the under part of the skull. Corresponding “bullæ” were noticed in the Rodentia, but in their case the swelling is in the temporal bone, whilst in the Marsupials, with the exception of the Wombat, they are formed out of the sphenoid bone (the great ala). Moreover, the Potoroos, like the Kangaroos, and some of the other Marsupials (the Phalangers and Koalas), have the ear chamber prolonged, by a number of cells, into the zygomatic process of the temporal bone. The Kangaroo-Rats are numerous, and there are many species. They are distributed in New South Wales, Western Australia, Van Diemen’s Land, and South Australia, and to the north-east.
