486 CAPE JUMPING HARE chap. 



Alactaga is much like Ui'chorcuics ; it has five toes, a 

 cylindrical tufted tail, tlie hairs at the end distichous, smooth 

 incisors, and a premolar present in the upper jaw. It also 

 differs from Unchoreutes hj the much smaller auditory Inilla as well 

 as in the fact that the infra-orbital foramen has no separate 

 passage for the nerve, w^hich passage is to be distinguished in 

 Ijoth DiiJus and Udchoreutes. The best-known species is the 

 Siberian Jumping Eabbit, A. Jaculus. Beneath the ends of the 

 three main toes of the feet are remarkable tan-shaped pads. In 

 A. decumana the l)ody and tail measure 7 and 10 inches re- 

 spectively, the ears 2 inches. Phttycaromys, a fourth genus of 

 the family, is much less known and is to be differentiated from the 

 last three genera by the fact that it has no premolars at all, the 

 grindino; tooth formula being thus '},. The tail too is flattened 

 and " lancet shaped." It extends from Siberia to Nubia, and 

 thus just enters the Ethiopian region. 



The above are the more typical Jerlioas. There remain 

 several forms which are not at all Jerboa-like in tlieir way of 

 life, but are nevertheless, on anatomical grounds, placed with 

 them. Zapiis, an American genus, with the exception of one 

 Palaearctic species, is transitional in that its hind-legs are 

 rather long, Ijut there is not so much difference between them as 

 in the typical Dipodidae. Smintlnis is at the opposite extreme 

 to Di'pus. Its feet are short and of equal length ; it climbs in 

 trees, and may perhaps be looked upon as nearest of all Dipodidae 

 to the ancestral form of the group. 



Fam. 8. Pedetidae. — The genus Fedetes contains but one 

 species, P. caffer, the Cape Jumping Hare. The animal suggests 

 a large Jerboa in appearance on account of its jumping habits, 

 the long hind-limbs, and the long tail. The length of a fair- 

 sized example is some 17 inches, with a tail of the same length. 

 The eyes and ears are large. The hands are five-fingered and 

 the feet only four-toed, the hallux being of course the absent 

 digit. In the skeleton it is interesting to note that the second 

 and third cervical vertebrae are so close together that there can 

 be no free movement ; interesting because in Dipvs the cervicals 

 are actually ankylosed. The dorsal vertebrae are twelve. The 

 small intestine is long, measuring 7 feet 4 inches, while the 

 caecum is short, l:)eing only 8 inches long. The large intestine 

 is 3 feet 10 inches long. The gall-bladder appears to be 



