RODENTIA. 87 



single bone, resembling what is called the tarsus in birds. It is from this dis- 

 proportion of the limbs that they were named by the ancients biped rats, and 

 in fact they seldom move otherwise than by great leaps on their hind feet. 

 There are five toes to each of the fore feet; and in certain species, besides the 

 three great toes to the hind feet, there are small lateral ones. They live in 

 burrows, and become torpid during the winter. 



D. sagitta. The jerboa has only three toes, and is the size of a rat ; a light 

 fawn colour above; white beneath; tuft of the tail black, the tip white. Is 

 found from Barbary to the north of the Caspian Sea. 



HELAMYS, F. Cuvier. PEDETES, Illiger*. 



The Jumping Hares, like the Jerboas, have a large head and great eyes, a 

 long tail, and the anterior part of the body extremely small, in comparison to 

 the posterior, although the disproportion is much less than in the true Jerboas. 

 The pecuh'ar characters of the Helamys are four grinders every where, each 

 one composed of two laminae; five toes to the fore-feet, armed with long and 

 pointed nails, and four to their great hind ones, all separate, even to the bones 

 of the metatarsus, and terminated by large nails, almost resembling hoofs. 

 This number of toes is the inverse of that most common among the rats. 

 Their inferior incisors are truncated, and not pointed like those of the true 

 Jerboas, and of the greater part of the animals comprised under the genus of 

 rats. One species only is known, the 



H. Coffer. It is the size of a hare, of a light fawn colour, and has a long 

 tufted tail, with a black tip. Inhabits deep burrows at the Cape of Good Hope. 



SPALAX, Gulden. 



The Rat Moles have also been very properly separated from the Rats, 

 although their grinders are three in number, and tuberculous, as in the true 

 Rats, and the Hamsters, and are merely a little less unequal. Their incisors, 

 however, are too large to be covered by the lips, and the extremities of the 

 lower ones are trenchant, rectilinear, and transverse, not pointed. Their legs 

 are very short ; each foot has five short toes, and as many flat and slender nails. 

 Their tail is very short, or rather there is none ; the same observation applies 

 to their external ear. They live under ground like the moles, raising up the 

 earth like them, although provided with much inferior means for dividing it; 

 but they subsist on roots only. 



S. typhus. (The Zanni, Slepez, or Blind Rat-Mole.) A singular animal, 

 which, from its large head, angular on the sides, its short legs, the total absence 

 of a tail and of any apparent eye, has a most shapeless appearance. The eye is 

 not visible externally, and we merely find beneath the skin a little black point, 

 which appears to be organised like one, but which cannot serve for the purpose 



Pedctes, Jumper; Hclamys, Jumping-Rat. 



