674 MR. R. I. POCOCK ON THE EXTERNAL 



Again, the claws are broad and strong like pointed lioofs, and 

 beneath are completely fused with the digital pads, which are 

 represented merely by an ill-defined area constituting the heel 

 of the hoof. I can find no trace of plantar pads, although Tull- 

 berg describes one at the base of each digit. All that I can find 

 is an elevation at the base of each digit formed by the underlying 

 bone. That, however, does not constitute a pad. The middle 

 area of the foot behind the base of the digits is provided with a 

 mat of long hairs which functionally takes the place of the 

 plantar pad. Behind this the sole is naked up to and including 

 the heel. (Text-fig. 35, D-F.) 



Good chai-acters foi- distinguishing the families, subfamilies, 

 and the principal genera are supplied by the hind feet : — 



a. Claws broad and lioof-like; digital pads scarcely developed, merelj^ 

 forming an ill-defined lieel to the hoofs ; plantar pads suppressed, 

 their place taken bj' a mat of hairs above the base of the digits ... Pedetes. 

 a'. Claws sharp and curved, not hoof-like ; digital pads normally or 

 exceptionally developed; plantar pad present, the middle of the 

 foot above the base of the digits naked. 

 b. Foot with separated metatarsals, "murine," artiodactyle or nearlj' 

 so ; plantar pad represented by four interdigital papillae ; hallux 

 much smaller than fifth digit and higher up the foot, the fiftli 

 at least reaching the base of the fourth ; digital pads normal. 



c. Foot short with digits 2 to 5 subequal, subequally spaced, and 



terminally almost in a line ; plantar and metatarsal papillse 



comparatively large Sicista. 



c'. Foot long, with third and fourth digits terminal and close 

 together, the second farther from the third, and the fifth still 

 farther from the fourth ; plantar and metatarsal papillaa 



minute Zapus. 



I)'. Foot with three median metatarsals fused, very long, not "murine," 

 markedly' perissodactyle ; plantar pad represented by a single 

 median conical papilla ; hallux, when present, as large as the fifth 

 digit and set on the same level, so high up the foot that their tips 

 fall far short of the bases of the adjoining digits ; digital pads of 

 second to fourth large, deep, compressed, and deeply grooved 

 laterally. 



d. Fifth digit retained ; short fringes of hair on digits 2 to 3 ; 



plantar papilla very large and exposed *. 



e. Fn-st digit (hallux) retained AUactaga. 



e' . First digit (hallux) absent Scartwus. 



d'. Fifth digit absent ; long fringes of hairs on digits 2 to 3 : plantar 

 papilla verj' small, normally concealed by overfolded fringes 

 of hair Jaculus, Scirfopoda. 



Tails. 



In Sicista and Zapus the tail is long, subcylindrical, tapering, 

 and covered with scales and short hairs as in typical murine 

 Rodents, the hairs at most forming a slight terminal pencil. In 

 the majority of the Jaculidse it is more definitely quadrate, 

 covered with short hairs, not distinctly scaly, and is provided 

 with a distinct terminal tuft, which, however, varies considerably 

 in size. In Jaculus jaculus, Scirtopoda orientalis, and Scarturus, 



* The hairiness of the feet in JUacfac/a may vary specificallj' according Iq 

 habitat, 



