REPORT ON THE MARSUPIALIA. 15 



In the Thylacine (PL I. fig. 5, c.d.) the fleshy belly divides high in the forearm 

 into three slips, from which three tendons issue. On the dorsum of the manus each 

 tendon splits into two, and each part is inserted into the dorsal expansion on the first 

 phalanx of the various digits ; thus the first tendon (enumerating them from the radial 

 side), by means of its two slips, goes to the index and medius, the second to the medius 

 and annularis, and the third to the annularis and minimus. In this manner, therefore, 

 the medius and annularis each receive two tendinous slips from the common extensor, 

 whilst the index and minimus only obtain one. 



In Cuscus (PL II. fig. 5, c.d.) and Phascogale the common extensor gives off four 

 tendons. On the dorsum of the manus these communicate freely with each other, and go 

 one to each of the four ulnar digits. 



In the Koala Young 1 stabs that the common extensor gives a tendon to each of the 

 five digits. This must be regarded as exceptional, because in the great majority of 

 Marsupials its insertion is limited to the four inner digits. 



Extensor digitorum secundus (Pis. I. and II. fig. 5, r.l.). — This muscle is undoubtedly 

 the representative of the extensor mimimi digiti in man. It is essentially the same in 

 each of the three animals. Arising from the external condyle of the humerus its tendon 

 splits into two parts on the dorsum of the manus, and these go to be inserted into the 

 dorsal expansions on the back of the annular and little digits. 



Macalister 2 gives some interesting information regarding this muscle. In the 

 AVombat, Opossum, and Pha.la.nger it supplies tendons to the annular and little digits ; in 

 the Tasmanian Devd, Bennett's Kangaroo, and the Giant Kangaroo to the medius, 

 annularis, and minimus. 



Extensor carpi ulnaris.- — In the large male TJiylacinus (PI. I. fig. 5, cm. and m.u.), 

 and in the Phascogale this muscle was split up into two distinct factors, which are 

 inserted respectively into the unciform bone, and the ulnar face of the base of the fifth 

 metacarpal. In the female Thylacine and in Cuscus (PI. II. fig. 5, c.u.) there was a 

 a single ulnar extensor muscle inserted into the metacarpal of the minimus. 



Extensor ossis metacarpi pollicis. — In the Cuscus this muscle has a very extensive 

 origin from the extensor surfaces of both bones of the forearm in their upper two-thirds, 

 and from a corresponding portion of the interosseous membrane. It divides into two fleshy 

 slips, which emerge in the interval between the common extensor and the short radial 

 extensor, and end in tendons (PI. II. fig. 5, c.r. and??t.r.) which wind round the radial 

 border of the forearm to be inserted into the trapezium, and into the base of the 

 metacarpal bone of the pollex respectively. 



In the Thylacine (PL I. fig. 5, c.r. and m.r.) the two portions of the muscle are 

 separable throughout their whole extent. That which is inserted into the metacarpal 

 bone arises from the middle third of the radius, whilst that portion which goes to the 



1 Jour. Anat. and Flip., vol. xvi. 2 Annals and Magazine of Natural History, vol. v. 



