878 DR. C. i\ SONNTAG ON THE MYOLOGY 



prolongations to the fifth metacarpal and the unciform in Phasco- 

 lat'ctos. 



Flexor Suhlimis Digitorum : — -This muscle is frequently strongly 

 connected to the flexor profundus, and it is sometimes called the 

 flexor perforatus because the profundus tendons pierce its tendons, 

 which are very slender. The sublimis and profundus tendons 

 separate out from the strong flexor mass in the distal part of the 

 forearm. 



Pronator Quadratus : — The extent of the interosseous space 

 occupied by the pronator quadratus varies considerably. In 

 Phascolomys I observed it extending over the distal half of the 

 space, but Macalister says it is weak and only occupies the distal 

 third. In Phascolarctos it occupies the lower fifth, but the extent 

 is even less in Phcdanger and Pseudochirus. Cunningham (2), 

 however, described it as covering one third of the bones in Cuscus 

 (Phalangista inaculata). 



Supinator Longus : — My observations on Phascolarctos difier in 

 some respects from those of Macalister (5) and Young (14). It 

 consists of two parts. The proximal division arises from the 

 shaft of the humerus from close to the neck downwards, and it is 

 thin and almost aponeurotic. The distal pait, which is more 

 muscular, arises from the lateral supracondylar ridge and by 

 fibres which fuse with the extensors of the wrist. The two parts 

 unite into a strong tendon which, passing under the abductor 

 pollicis major, is inserted into the scapho-hmar bone. Young 

 points out that it is both a radial flexor and supinator. It receives 

 a slip from the deltoid. In Phalanger it is also large, but not 

 divided into two parts. It springs from the proximal two-thirds 

 of the lateral supracondylar ridge. No slip runs into it from the 

 deltoid. These conditions are also present in Pseudochirus. The 

 conditions in Phascolomys are, however, vei-y difierent. It is 

 thin and aponeurotic in parts, and it receives a strong band from 

 the deltoid. 



Supinator Brevis : — The extent of the radius embraced by this 

 muscle varies. In Phalanger it covers less than the upper fifth, 

 in Phascolarctos it covei-s the upper fifth, and in Phascolomys it 

 envelops the upper two-thirds, 



Extensores Carpi Radiales : — The existing records show that 

 there is considerable variation in these muscles in the Marsupialia. 

 1x1 Phascolomys there is a single muscle arising from the external 

 condyle and lateral ridge of the humerus and running to be 

 inserted into the second and third metacarpal bones. But it is 

 evident that the long and short extensors are combined in the 

 single muscle. In Phascolarctos both long and short extensors are 

 present and are inserted into the radial borders of the second and 

 third metacarpals respectively. In Phalanger both muscles are 

 present, but the brevior is a large and powerful muscle with 

 three heads of origin as described by Cunningham (2). 



Extensor Communis Digitorum : — In all forms it arises from 

 the external condyle. In most Marsupialia it sends four tendons 



