GEEBILLUS GERBILLUS. 
253 
nearly straight or very slightly concave; posterior margin nearly vertical in its upper 
half, hut gradually rounded off into the upper margin. The ear laid forwards reaches 
to the anterior angle of the eye, or nearly so. The fore limb is short, the length from 
the elbow to the tip of the middle finger falling short of the distance between the heel 
and the end of the fifth toe. Fingers moderately long, the third the longest, the second 
slightly shorter than the fourth, the fifth considerably shorter than the second ; the 
first reduced to a rudiment, consisting chiefly of the flattened nail. On the palm there 
is a swollen eminence with a prominent tubercle behind it, larger than the thumb 
which it resembles. This eminence and the under surfaces and sides of the fingers 
are covered with rather strong pure white hairs, those on the centre of the fingers 
directed forwards and those on the sides curving downwards. The claws are rather 
long and not much curved, the third being the longest. The lower third of the 
radial portion of the arm and the upper surface of the hand are clad, but not very 
densely, with pure white hairs. 
The hind foot, considering the size of the animal, is rather powerful, and the toes are 
long, the third toe in length equalling one-half of the distance between its base and 
the heel. The third and fourth toes are of equal length, or one may be a little longer 
than the other. The second is shorter than either of them, and the fifth only reaches, 
without its claw, to the penultimate joint of the fourth. The end of the claw of the 
hallux reaches only to the penultimate joint of the second toe. There is an anteriorly 
four-lobed swollen eminence in the centre of the sole, the four lobes corresponding 
to the bases of the first, the second, the third, and the fourth and fifth toes; this 
eminence is well clad with hairs directed forwards, and the sides of the toes with 
longish, stitfish hairs, curving downwards and forwards, to a much greater extent 
than in the manus. No tarsal tubercle is present. The whole of the tarsus, except 
a narrow linear area at the heel, is sparsely clad with short white hairs, and the lower 
half of the tibial portion of the leg and the upper surface of the foot are covered 
with short fine white hairs. The skin of the tail is annulated as in mice, but the rings 
are hidden by the short hairs which clothe it. Towards the end of the tail the hairs 
gradually become longer, reaching 12 mm. in length, so that it terminates in a 
pronounced pencil of hairs. The short hairs on the upper surface of the tail are rich 
fawn-coloured, those on the lower surface silvery white, but as they become longer to 
form the pencil, those on the dorsum form a narrow line of blackish hairs. The hairs 
of the pencil are adpressed to the tail except in the case of the blackish-brown hairs, 
which are semi-erect. 
The only portion of bare skin on the snout is a middle area immediately above and 
below the nostrils, which are placed transversely. There is no cleft towards the incisors, 
the front of the muzzle being covered with short white hairs. The moustachial hairs 
are numerous and long, directed outwards, the majority of them being white. 
