17 1 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



point above; the anterior third is folded close hack. The back of the ear 

 and the fold of the conch arc sparsely pilous; the exposed parts of the fronl 

 of the ear being more thickly clothed. The antitragal pad bears on its outer 

 surface a special tufl of long hairs; its other side being naked, as are both 

 sides of the flap of the tragus. 



The lore limbs are absolutely small, as well as short in comparison with 

 the hinder ones: and they seem to he 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 Hat, 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, &c, is especially notice- 

 able in the pes, which exceeds the cms 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 Mas) for about half- 

 wav, then granular; the dibits 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 tour 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 live 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 liases of the lateral digits. 



