46 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. XIV. 



Extensor indicis. Origin from the antero-external edge of the 

 ulna opposite the greater sigmoid cavity. Its tendon divides into two 

 about midway of its length. These pass under the digital extensors and 

 across the carpus to insertions one at the base of the ungual phalanx of 

 the first digit and one at the same point on the second digit. 



MUSCLES OF THE FOREFOOT. 



The delicate intrinsic muscles of the forefoot have been worked out as 

 carefully as possible, but in all the specimens examined some of the 

 metacarpal bones were found to be broken, making it very difficult to 

 ascertain exact relations. In general the muscles of the hand differ from 

 those of Didelphis more than they do from some of the Australian forms. 

 The adductors are much less highly developed than in Didelphis and 

 this in connection with the absence of a pronator quadratus indicates a 

 relatively limited power of action of hand and fingers. 



Lumbricals are present but not greatly developed. 



Adductors. Three adductors are readily distinguishable, the 

 indicis, annularis, and minimus. They arise in the palmar fascia at the 

 base of the metacarpals and radiate to their insertions as practically 

 separate muscles without any development of a central raphe. The 

 indicis arises over the bases of the second and third metacarpals and 

 inserts on the ulnar side of the distal extremity of the second metacarpal. 

 It is separable with some difficulty from the ulnar head of the flexor 

 brevis indicis. The annularis and minimus arise over the bases of the 

 third and fourth metacarpals and insert on the radial sides of the distal 

 ends of the fourth and fifth metacarpals respectively. They are sep- 

 arated from the flexors by a large palmar nerve. An adductor pollicis 

 could not be distinguished. In general the adductors seem to be very 

 similar to those of Thylacinus as figured by Cunningham. 



Flexors. Short flexors are well developed on all the fingers. The 

 flexor brevis pollicis could not be divided into two parts. It arises on 

 the ulnar side of the base of the first metacarpal and inserts medially 

 with a sesamoid at the first joint of the pollex. It is a relatively thick 

 muscle and possibly may include a fused adductor. A rather definite 

 aponeurotic strand running from the carpus to the ulnar side of the first 

 joint of the pollex may represent a second head of this flexor. The re- 

 maining flexors are divided except proximally and lie in the usual posi- 

 tion on the metacarpals with their tendons of insertion embracing the 

 metacarpo-phalangeal joints of each of the digits. 



Abductors and inter ossei. Two marginal muscles regarded re- 

 spectively as abductor pollicis and abductor digiti minimi are present. 



