172 ANATOMY OF THE WOOD RAT 



There is a pair of metatarso-phalangeal sesamoid bones 

 to each digit, at the joint and in the position indicated in 

 the illustrations. 



There are two phalanges in the first digit and three in each 

 of the other four. Of the latter, the proximal phalanges 

 are longer than the second, while the terminal phalanx 

 of each digit is minute, serving as a support for the claw. 

 They can not be examined without disarticulation and care- 

 ful cleaning. 



As previously mentioned, the distal extremities of some 

 of the tendons are so tenuous that the precise points at which 

 they are inserted upon the digits are in doubt. Upon digit 

 one are inserted tendons of the flexor digitorum longus, 

 flexor fibularis, and extensor hallucis. Upon digits two and 

 three, the extensores digitorum brevis and longus, plantaris, 

 and flexor fibularis. On digit four, the plantaris, flexor 

 fibularis, extensor digitorum longus, and peroneus digiti 

 quarti. The same are attached to digit five, except that the 

 peroneus digiti quinti takes the place of the peroneus quarti. 

 The only appreciable subgeneric differences shown are that 

 in Teonoma a branch of the plantaris extends also to digit 

 one, and the peroneus digiti quarti sends two branches, in- 

 stead of one, to digit four. This difference is probably not 

 sufficient to prove of much functional importance to the 

 animal. 



