ORDER RODENTIA. fc . , 145 



the Alactaga, which has thirty-one. The bones of the first 

 are in general stronger. The caecum is shorter, and scarcely 

 reaches the symphysis of the pubis. Of the three toes of 

 the Gerbo, that in the middle is scarcely larger than the 

 two others. Of the five toes of the Alactaga, the middle is 

 considerably longer than the lateral toes, which are re- 

 moved back as far as one-third of the length of the meta- 

 tarsus. 



The Gerbos are very common in Barbary, in Egypt, in 

 Syria, and Arabia. But their species is proportionally less 

 numerous as we advance to the north. Nevertheless it 

 does extend in that direction as far as the countries situ- 

 ated between the Tanais and the Volga, as far as 50° north 

 latitude. It was in this country that Pallas discovered his 

 Mus Sagitta. In this country these animals are less nume- 

 rous than the Gerboas, of which Pallas makes a third vari- 

 ety of the Alactaga or Mongul. But they are found in con- 

 siderably numbers in the sandy hillocks which border the 

 southern banks of the Irtish. 



Egypt is the country in which Gerbos have been observed 

 with most facility. The sands and ruins which environ 

 modern Alexandria, are, says Sonnini, very much fre- 

 quented by these animals. They live there in troops, and 

 form burrows which they dig with their nails and teeth. It 

 is said that they can pierce through the small stones which 

 are below the bed of sand. Without being exactly feroci- 

 ous, they are very unquiet animals. The least noise makes 

 them re-enter their holes with precipitation. They can 

 only be killed by surprising them. The Arabs know how 

 to take them alive, by closing up the issues of the different 

 galleries of their burrows, with the exception of one 

 through which they must go out. Their flesh, though not 

 the best of meat, is yet in considerable request among the 

 Egyptians. Their skins, the hair of which is soft and 

 shining, is employed in the manufacture of ordinary furs t 



