u 4 RODENTS, 



tufted tail being black near the end, but white at the extreme tip. The length of 

 the head and body is 3J inches, and that of the tail 6J inches. 

 Broad-Tailed Certain species of jerboas inhabiting the desert regions of Central 



Jerboas. an( J Northern Asia and Nubia are distinguished from those of the 

 two preceding genera by their flattened and lancet-shaped tails, in consequence of 

 which they have received the name of Platycer corny s. They are further dis- 

 tinguished by the absence of premolar teeth in both jaws. There is nothing worthy 

 of special notice in the habits of these species. 



THE THREE-TOED, OR TRUE JERBOAS. 







Genus Dipus. 



The true jerboas, as typically represented by the common Egyptian species 

 (Dipus jaculus), are the most specialised representatives of the subfamily, having 

 completely lost the two small lateral toes on the hind-limbs. They are further 



EGYPTIAN JERBOA. 



distinguished by the presence of vertical grooves on the front of the incisor teeth ; 

 while they have a pair of premolar teeth in each jaw. They resemble the alagdaga 

 in the great length of the hind-limbs and tail, and the comparatively large size of 

 the ears ; the tuft of hair at the tip of the tail is, however, smaller. Usually the 

 premolar teeth are wanting. 



In size, the Egyptian jerboa is rather inferior to the alagdaga, the length of the 

 head and body being about 6| inches, while the tail, exclusive of the hairs at the 

 end, measures a little over 8 inches. The general colour of the upper-parts is a 

 sandy grey ; the under surface of the body being white, and a broad white stripe 

 extending down the hind-limbs. The tail is yellowish brown above and whitish 

 beneath, with the usual black-and-white tip. 



The range of the Egyptian jerboa extends from the north of Arabia westwards 



