RODENTS. 
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tufted tail being black near the end, but white at the extreme tip. The length of 
the head and body is inches, and that of the tail 6i inches. 
Broad-Tailed Certain species of jerboas inhabiting the desert regions of Central 
Jerboas. and 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 Platycercornys. 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 
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 6f 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 
