RODENTIA. 97 



It is from this disproportion of the limbs that they were named by the an- 

 cients 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 tliree 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. Cuv. — Pedetes, Illig.(l) 

 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 compari- 

 son to the posterior, although the disproportion is much less than in the 

 true Gerboas. The peculiar 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 fonr 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 tlie inverse of that most 

 common among tlie Rats. Their inferior incisors are truncated, and not 

 pointed like those of the true Jerboas, and of the greater part of the ani» 

 mals comprised under the genus of Rats. One species only is known, the 

 H. Caffer. 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, al- 

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

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

 sors, however, are two 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 sliort toes, and as many flat and 

 slender nails. Their tail is very short, or rather there is none; the same 

 observation applies to their extei-nal ear. They live under ground like the 

 Moles, raising up the earth like them, although provided with much infe- 

 rior means for dividing it; but tliey 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 can- 

 not serve for the purpose of vision, since the skin passes over it without 

 opening or even growing thinner, and being as much covered with hair as 



(1) Petfefes, jumper; Helamys, Jumping-Rat. 



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