REPORT ON THE MARSUPIALIA. 



23 



These muscles have the same insertions as the corresponding muscles in Phascogale. 

 They all arise from the front of the carpus — the adductors of the ring finger and index 

 by a common tendon (fig. 3, a.b), and partly under cover of the origin of the adductor 

 minimi digiti (fig. 3, c.) The adductor of the thumb is fused with the ulnar portion of 

 the flexor brevis pollicis, but in one dissection it was readily separated as a distinct and 

 exceedingly slender slip, having the same attachments as in the Phascogale. 



The intermediate group of muscles (figs. 1 and 3, g 1 tog 6 ) corresponds in all respects 

 with the same muscles in the Phascogale. At first sight they seem more complicated 

 in their arrangement from the accessory slips of the dorsal interossei being associated 

 with them. 



(>l>ponens pollicis. — This muscle is only present in the form of a few fibres, which 

 pass from the conjoined abductor pobicis and radial part of the flexor brevis pollicis to 

 the metacarpal bone. 



The Palmaris brevis is very strongly marked. It cannot be considered as belonging to 

 any one of the three groups of intrinsic muscles. It consists of two fleshy slips, both of 

 which arise from the superficial aspect of the annular ligament. The smaller of these is 

 inserted into the flexor sheath of the little finger, whilst the larger is attached to the 

 ulnar side of the base of the first phalanx of the same finger. 



Cuscus (PL II. figs. 2-3). 



The abductors of the little finger (fig. 3, d) and thumb (fig. 3, e) are both present 

 The former is more strongly developed than the latter, which is more or less completely 

 fused with the radial head of the flexor brevis pollicis. 



The four dorsal interossei differ somewhat in their relative sizes and mode of origin 

 (fig. 2). The first, or abductor indicis (d l ) is very small, and consists of a single fleshy 

 band, which arises from the palmar surface of the base of the metacarpal bone of the 

 thumb, and is inserted into the radial side of the first phalanx of the index. The other 

 three cannot be said to occupy the intermetacarpal spaces, inasmuch as they arise entirely 

 from the dorsal surfaces of the metacarpal bones. The second (c/ 2 ) is the largest, and 

 arises by two parts from the second and third metacarpal bones ; the third (d s ) springs 

 from the metacarpal bone of the ring finger ; and the fourth (J 4 ) from the metacarpals 

 of the ring and little fingers. They are inserted as in man, with the exception of the 

 third, which, like the same muscle in the Thylacine, is inserted into the bases of the two 

 fingers, between which it lies. Whdst the other dorsal interossei act as abductors of the 

 fingers, the third approximates, and then extends the ring and middle fingers. 



In the Cuscus there is a very beautiful arrangement by means of which the abducting 

 power of these muscles is increased. The tendon of insertion of each muscle, with the 

 exception of the abductor indicis, is fixed by a little transverse fibrous band to tin- head 



^°°c 



