There are three or four diftinift fpecies, or at leaft 
permanent varieties of Jerboa, and in the Hiftory of 
Quadrupeds of Mr. Pennant they conftitute a parti¬ 
cular genus ; but Linnaeus places them as fpecies of 
the genus Mas. 
The Jerboas are animals of the moil furprizing fwift- 
nefs, and on the approach of danger immediately 
fpring forward by fucceffive leaps, fo very nimbly, that 
it is faid to be very difficult fora man well mounted to 
overtake them. They are impatient of cold, and re¬ 
main during the winter in a dormant ftate in their bur¬ 
rows. They feed on vegetables. The particular fpe¬ 
cies here reprefented differs principally from the com¬ 
mon Jerboa or Mus Jaculus of Linnaeus in having the 
legs furniffied at a little diftance above the feet with a 
jsair of fpurious toes or fpurs. It is found not only in 
the warmer regions of Barbary and Syria, but in the 
Eaftern part of Siberia in considerable plenty. It is 
about the fize of a large rat. 
