ore-limbs very small; hind limbs long and strong,
with from three to five digits; tail long, hairy. Three sub-families"
(_Alston_ On the Order GLIRES, 'P. Z. S.' 1876). The three
sub-families are _Zapodidae_,[28] _Dipodinae_ and _Pedetinae_, but
we have only to deal with the second.

[Footnote 28: Formerly _Jaculinae_.]

[Illustration: Dentition of Jerboa.]

_GENUS DIPUS--THE JERBOAS_.

Hind feet with three digits; tail cylindrical and tufted; incisors
grooved; premolars absent, or, if found, then in the upper jaw and
rudimentary; skull with very broad occipital region; greatly
developed auditory bullae; the cervical vertebrae are more or less
anchylosed, and the metatarsals are united. They are not found in
the plains of India, though one species inhabits Yarkand, and two
more are found in Eastern Persia.

[Illustration: _DIPUS_.]

NO. 400. DIPUS LAGOPUS.
_The Yarkand Jerboa_.

HABITAT.--Koshtak, south of Yarkand; Yarkand; and
Yangihissar.--_Blanford_.

DESCRIPTION.--"Colour above light sandy brown, slightly washed with
dusky, below pure white; a white band across the outside of the thigh;
tail pale brown above, whitish below, with a tuft of longer hair,
altogether about 2-1/2 inches long; at the end the terminal portion
pure white, the proximal portion black or dark-brown on the upper
part and sides, but brown or white beneath the tail. The fur is very
soft and rather long, 0.6 to 0.8 inch in the middle of the back; on
the upper parts it is ashy grey at the base and for the greater parts
of its length, pale sandy brown near the end; the extreme tip dusky
brown; on the lower parts it is white throughout; ears about half
the length of the head, oval, naked inside, thinly clothed with short
brown hair outside; face sandy; the hairs grey at the base; sides
of head whitish; whiskers as usual very long, exceeding three inches;
the uppermost brown; the longest white, except at the base; the lower
entirely white; the long hairs beneath the hind feet all white, as
are the feet throughout."--_Blanford_, 'Sc. Res. of Sec. Yarkand
Mission,' pp. 58,59.

_GENUS ALACTAGA_.

"Hind feet with _five_ digits, of which the first and fifth do not
reach the ground; tail cylindrical, tufted; skull with the occipital
region less broad, and the auditory bullae smaller; infra-orbital
opening with no separate canal for the nerve; incisors plain. One
very small premolar present above only."--_Alston_.

NO. 401. ALACTAGA I