JERBOA, a family of rodent mammals (Dipodidae), chiefly characterized by the great length of the hind limbs as compared with those in front, the disproportion being, in most cases, greater even than in the kangaroos. Like the latter, the jerboas, or jumping mice, as they are also called, raise themselves when disturbed on their hind legs, and execute enormous leaps by the aid of a long muscular tail. When undisturbed, however, they make use of all their limbs in walking, while the front pair are also employed by many species as hands for the conveyance of food to the mouth. The jerboas, of which there are three genera and twenty-two species known, occur chiefly throughout northern and central Africa, south-eastern Europe, and central and southern Asia, while one genus (Pedetes) is confined to South Africa and another (Jaculus) to North America. Of the third genus (Dipus) there are twenty known species, a typical example of which is the Egyptian jerboa (Dipus segyptius). The length of its body is 8 inches, and of its tail, which is long, cylindrical, and covered with short hair, terminated by a tuft, 10 inches. Its front limbs are pentadactylous, and only 1 inch in length, the hind pair three-toed and six times as long. When about to spring, it raises its body by means of the hinder extremities, and supports itself at the same time upon its tail, while the fore feet are so closely pressed to the breast as to be scarcely visible. Hence probably the name Dipus, or two-footed. It then leaps into the air and alights upon its four feet, but instantaneously erecting itself, it makes another spring, and so on in such rapid succession as to appear as if rather flying than running. It is a gregarious animal, living in considerable colonies in burrows, which it excavates with its ...