104 
MAMMALIA. 
There is a black variety, with a little white round the mouth, 
on the nose, edge of the ears, feet, and extremity of the tail. 
Genus 13. —Dipus. — Cuvier. 
Generic Character _Incisors no canines, grinders or 
total 1G or 18. Lower incisory teeth sharp pointed; grinders 
simple, with tuberculous crowns ; eyes large; ears long and 
pointed; fore feet short, with four toes, and a tubercle in place 
of a thumb, which is furnished with a nail ; the hind feet are 
five or six times longer than those before, with three or five 
toes, having one metatarsus for the three middle toes; tail very 
long, generally tufted. 
Dipus sigitta. — The Common Jerboa. 
Plate XVIII. fig. 6 . 
Fur bright yellow above, white underneath ; with a dusky, 
semilunar band across the upper part of the rump; tail longer 
than the body, with an oblong dusky tuft at its extremity; white 
at the tip. Body about six inches. Inhabits Barbary, Egypt, 
and Western Asia. 
Genus 14. —Gerbillus. — Desmarest. 
Generic Character. —Incisors |, no canines, grinders jH?; to¬ 
tal 1G. Grinders tuberculous; the first with three, the second 
with two, and the third with one tubercle ; ears moderately sized ; 
fore feet short, with four toes, and a rudimentary thumb; the 
hind legs very long, having five toes with nails; each foot with 
a proper metatarsal bone ; tail long, covered with hair. 
Gerbillus Canadensis. — The Canada Gerbil. 
Plate XIX. fig. 11. 
Fur yellowish above, white underneath; ears short \ tail with 
hardly any hair, somewhat longer than the body ; without any 
tuft- Inhabits Canada, in the neighbourhood of Quebec. 
