MOLE-RAT.
The other section of the Mole rat family, the BATHYERGINÆ, is entirely confined to Africa, and, indeed, almost exclusively to the southern extremity of that continent, only a single species being found elsewhere—at Mozambique. They show a resemblance to the Hystricine Rodents in the structure of the lower jaw, the angular portion of which springs from the side of the bony case of the lower incisor; and the palate between the molars is narrower than in the Spalacinæ. The best known of the six species inhabiting the Cape of Good Hope is the STRAND MOLE-RAT (Bathyergus maritimus), which is nearly as large as a small Rabbit, its length being about ten inches, with a tail two inches in length. In general form it resembles the species last described; it has small but uncovered eyes, a broad nose, no external ears; very long, compressed, and powerful claws on all the toes, except the thumb of the fore-feet, which has a crooked nail; four molars on each side, and long white incisors, of which the upper ones are strongly grooved in front. The colour of the fur is greyish-white, with a yellowish tint on the upper surface. The tail has a sort of radiating tuft of hairs at the end. The Strand Mole-rat lives entirely in sandy localities near the sea-shore, and especially in the sand-hills or dunes which fringe the coast of the Cape of Good Hope in some parts. Here it burrows freely in all directions, its galleries generally radiating from several central points, and joining in various places. It avoids the light as much as possible, and if by chance it is exposed on the surface it is exceedingly helpless. Very little is known of the habits of this species, which probably feeds chiefly on roots like the other members of the family. It is regarded as mischievous, as it undermines the ground so much as to make it unsafe to ride over. The colonists, therefore, often destroy it by various means. The enamel folds of the teeth become effaced with use.
The Georychi, five species of which inhabit Cape Colony, resemble the preceding species, but are smaller and weaker. The claws of the fore-feet are shorter and weaker, and the upper incisors, which are long and arched forward, are not grooved. The best-known species is the so-called CAPE MOLE-RAT (Georychus capensis). In the Mozambique species (Heliophobius argenteo-cinereus) there are six molars on each side above and below, and the second toe of the hind feet is the longest. In most other characters it resembles Georychus.
FAMILY IX.—GEOMYIDÆ, OR POUCHED RATS.
The Pouched Rats, or Pocket Gophers, and the Pouched Mice of North America, constitute a family distinguished from all the preceding forms by the presence of a pair of great cheek-pouches, opening outside and not inside the mouth (see figure). These cheek-pouches are hairy inside throughout. The angular portion of the lower jaw is strongly twisted, the molars are four in number on each side in each jaw, and the squamosal bone is very large. In external characters the animals of this family present considerable diversity, which has led to their being divided into two well-marked sub-families, the distinctive peculiarities of which are of such importance that Dr. Coues has raised them to the rank of distinct families. The GEOMYINÆ, or Pouched Rats, are more or less Rat-like animals, in which the feet are five-toed, and all the toes furnished with claws, those of the fore feet being very strongly developed; and the tail is short. Certain other characters are presented by the skull. The outline of this part, including the zygomatic arches, is almost quadrangular; the infra-orbital opening is far in front of the jugal process; the malar bone extends forward to the lachrymal.
MOLAR TEETH OF THE MEXICAN POUCHED RAT.
UNDER SURFACE OF THE HEAD OF HETEROMYS.