474. MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
point above; the anterior third is folded close back. The back of the ear 
and the fold of the conch are sparsely pilous; the exposed parts of the front 
of the ear being more thickly clothed. The antitragal pad bears on its outer 
surface a special tuft of long hairs; its other side being naked, as are both 
sides of the flap of the tragus. 
The fore limbs are absolutely small, as well as short in comparison with 
the hinder ones; and they seem to be placed rather far forward, though this 
appearance may be due, in part at least, to the tapering shape of the body. 
The hands are pilous above, naked below. There are four perfect fingers, 
with ordinary claws, and a rudimentary thumb, which bears a flat, blunt nail. 
The third digit is the longest; the fourth, second, and fifth being successively 
shortened. The digits are regularly transversely scutellate below. The palm 
is granular throughout, with a pair of large smooth pads (inner and outer) 
near the wrist, and three smaller tubercles at the basesof the digits; two proper 
to the second and fifth, respectively, one common to the third and fourth. 
The elongation of the hind limbs, which confers the high degree of 
saltatorial power upon this animal, like-that of Dipus, &e., is especially notice- 
able in the pes, which exceeds the crus in length. This development of the 
foot, nevertheless, is not accompanied by reduction of the digits in number, 
nor by any imperfection of their respective metatarsals. The number of 
these bones has been queried: I find five, perfect from end to end, with com- 
plete tarsal and phalangeal articulations. The foot is clothed above with 
short, soft, silky hairs, quite different from the hirsute pelage of the body; 
below, it is entirely naked, though the lateral fringe of hairs encroaches upon 
the contracted heel. The sole is perfectly smooth (as in Mus) for about half- 
way, then granular; the digits are transversely scutellate underneath. There 
is a well-defined tubercle on the inner side a little distance above the base of 
the first digit, and four others at the bases of the digits; three proper to the 
first, second, and fifth, respectively, one common to the third and fourth. 
There are five perfect and normally-clawed digits. The first is shortest, and 
also situated rather high up, so that its tip reaches only to about the base of 
the second. The fifth is next longer, reaching the middle of the fourth. The 
third slightly exceeds the fourth and second, which are about equal to each 
other. There is much basal webbing between the three intermediate digits, 
especially between the third and fourth, which carries their apparent bases 
far beyond the bases of the lateral digits. 
