OF THi; WOMBaT, IfOALA, AND PHAtANGfiHS. 879 



to the four inner digits. But, as Young (14) mentions, and I 

 observed rayself, tendons go to each of the five digits in Phasco- 

 larctos. 



Extensor Seciijiidus Digitov'um : — This muscle, which corresponds 

 to the extensor minimi digiti of human anatomy, has been fully 

 described in many Marsupialia by Cunningham (2), Young (14), 

 and Macalister (5 & 18). In Phascolarctos it is in reality double. 

 One muscle runs to the third digit as an extensor medius, and 

 the other is inserted into the fourth and fifth digits. In Pliasco- 

 lomys and the Phalangers only the latter part is present. 



Extensor Carpi Ulnaris : — In Phascolomys it arises from the 

 external condyle of the humerus and upper part of the shaft of 

 the ulna, and is inserted into the mesial border of the shaft of the, 

 fifth metacarpal bone. In Phascolarctos the ulnar origin head is 

 similar to the above. But in Phalanyer there is no ulnar head. 



When a superficial view of the extensor muscles is taken in all 

 the animals described in this paper, it is seen that intermuscular 

 septa are well marked in Phascolarctos. In Phascolomys and the 

 Phalangers there is more fusion of the bellies of the muscles. 



Extensor Ossis Metacarpi Pollicis : — This muscle, as has already 

 been pointed out by several authors, includes the extensor primi 

 internodii pollicis. In Phascolomys, according to Macalister (18), 

 it ariises from the dorsum of the shaft of the ulna and the inter- 

 osseous membrane, crosses the extensor carpi radialis tendon, and 

 is inserted into the trapezium and thumb metacarpal. In Phasco- 

 larctos I observed it arising from the dorsum of the proximal 

 third of the part of the ulna bordering the interosseous space, 

 from the membrane, and from the greater part of the dorsum of 

 the radius from the orbicular ligament distally. In Phalanger 

 and Pseudochirus it also arises from both bones and the inter- 

 osseous membrane, but the ulnar origin is lower and more 

 extensive than in Phascolarctos, and the muscle belly gives ofll:" two 

 tendons which wind over the extensor carpi radialis and supinator 

 long us tendons. 



Extensor Secundi Internodii Pollicis : — There is no trace of this 

 muscle in Phascolarctos, and in this respect I agree with Young 

 (14) and diflfer from Macalister (5), who stated that it is arranged 

 as usual. In Phascolomys it runs from the lower third of the 

 ulna to the last phalanx of the poUex. The tendon gave a short 

 slip to the fascia over the metacarpo-phalangeal joint of the index. 

 In Phalanger it also gives slips to the index and pollex, and 

 Cunningham (2) describes two separate muscles in Phalangista 

 maculata. It is therefore evident that the only extensor of the 

 pollex in Phascolarctos is the additional tendon of the extensor 

 communis digitorum ; and in no other Marsupial is this arrange- 

 ment present. 



Intrinsic Muscles of the Manus : — -The observations of 

 Cunningham (2), Macalister (5, 18), Huge and Young (14, 15) 

 have given us a very complete account of the anatomy of these 

 muscles. Young, in particular, has shown how they have become 



