CHARACTERS OF SOME HVSTRICOMORrH RODENTS. 389 



Specialisation of the feet on the lines indicated in Erelhizon 

 is carried a stage further m Coencht, where an excrescence on the 

 inner side of the plantar area, giving greater width to the sole, 

 takes the place of the poliex, while a very mnch larger, nearly 

 semicircular expansion, occupying the whole length of the sole 

 of the hind foot, takes the functional place of the hallux *. This 

 expansion is movable up and down to a certain extent, and 

 enormously increases the supporting area and gripping power 

 of the foot. As in Erethizon, the plantar, carpal and metatarsal, 

 and the digital pads are covered with squamous papillae. (Text- 

 figs. 10, 11.) 



In the disposition and proportionate length of its digits the 

 fore foot of Mi/occcstor resembles that of GaprornT/s, but the four 

 main digits are relatively shorter and stouter, and have thicker 

 blunter claws. The pads are better developed, being relatively 

 larger and more cushion-like. The median lobe of the plantar is 

 approximately twice the size of either of the laterals, and there 

 is a deep or shallow division between the two elements of the 

 carpal pad. The radial moiety of the latter is also covered, like 

 the rest of the carpal pad, the plantar, and the digits, with squami- 

 form napillae. I found no trace of carpal vibrissje. (Text- 

 fig. 12, B.) 



The hind foot is very much larger than the fore foot t, mainly 

 owing to the elongation of the digits, of which the thiixl is the 

 longest, the second and fourth a little shorter and subequal, 

 the fifth considerably shorter than the fourth and the first than 

 the fifth. The first, second, third, and fourth are united by 

 swimming-webs extending up to the digital pads ; but the only 

 trace of web between the fourth and fifth is a fiap of skin 

 running along the inner edge of the fifth digit, which is thus 

 left free for the purpose, I believe, of acting more eflicaciously 

 as a skin-scraper. The plantar pad is indistinctly defined, being 

 represented by lobes of skin at the base of the first, second, 

 third, and fifth digits. The comparatively short metatarsus is 

 naked back to the heel. Its anterior portion, like the plantar 

 area and the digits, is covered with squamous papillae, but a 

 varying amount of the heel is smooth, especially on the outer 

 side. (Text-fig. 12, A.) 



The feet of Dactylomys and Cannabateoinys are very different 

 from those of the typical genera of Loncherinse. In 0. amhlyonya, 

 as figured by Winge and Tullberg, the lower sides of the digits 

 and soles are uniformly and closely covered, except on the heel, 

 with squamous papillse, lineally arranged on the digits, but show 

 no trace of definite pads apart from the integumental grooves 

 resulting from the folding of the digits on the soles. The fore 

 foot has a minute functionless poliex close to the base of the 

 second digit, which rises nearly on the same level as the fifth, 



* In a young example of C. preJiensilis there was a larger external hallux occupy- 

 ing the same position as the hallux in Erethizon. 

 t Precisely as in the Otters and for similar reasons. 



