18 THE VOYAGE OF H.M.S. CHALLENGER. 



Palmaris longus. — In the Thylacine this muscle has very little direct attachment to 

 the internal condyle of the humerus. It springs from the superficial aspect of the great 

 flexor muscle of the digits, and ends in a powerful tendon which penetrates into the midst 

 of the palmar pad. Here it breaks up into four strong slips which go to join the flexor 

 sheathes of the four ulnar digits. In Phase ogale the palmaris longus is arranged upon 

 a similar plan, but in the palm it spreads out into a distinct palmar fascia. 



In Cuscus there are three small muscular slips representing the palmaris longus, viz., 



(1) a very delicate fasciculus which springs directly from the internal condyle of the 

 humerus ; (2) a larger slip which arises in common with the great flexor of the digits ; (3) 

 and a deeper portion which issues from the superficial aspect of the flexor of the fingers. 

 They all proceed to join the palmar fascia. 



Flexor carpi ulnaris. — This muscle has a similar disposition in each of the three 

 animals. It is a broad thin band which gradually tapers towards the point from which the 

 tendon issues. As is customary in the majority of Marsupials it arises by two pointed 

 processes — one from the internal condyle of the humerus, and the other from the 

 olecranon process. Between these points it derives fibres from a strong fibrous arch 

 which bridges across the interval between those bony prominences. In the Thylacine 

 and Phascogale the lower border of the anconeus internus is in close apposition with this 

 fibrous arch ; in the discus it is inseparably united with it. The ulnar nerve enters the 

 forearm by passing downwards under cover of the anconeus internus and the fibrous arch 

 in question. In all the three animals the flexor carpi ulnaris is inserted into the pisiform 

 bone. 



Flexores digitorum. — The flexor sublimis, the flexor profundus, and the flexor longus 

 pollicis are in great part amalgamated in all the animals under consideration. 



In Cuscus the great flexor mass arises in three parts, which in all probability represent 

 the three factors which enter into its constitution. These may be termed (l) the radial, 



(2) the ulnar, and (3) the condylar. 



The condylar portion is intermediate and superficial, and is probably the representa- 

 tive of the flexor sublimis. It arises from the internal condyle of the humerus. The 

 radial portion springs from the anterior surface of the radius from the tubercle above to 

 about the middle of the bone below. It lies under cover of the large pronatorradii teres, 

 and represents the flexor longus pollicis. The ulnar subdivision takes origin from the 

 ulnar surface of the olecranon under cover of the anconeus internus, and from the 

 posterior border and ulnar surface of the shaft of the ulna in its upper half, under cover 

 of the flexor carpi ulnaris. This portion apparently represents the flexor profundus. 



The three subdivisions of the muscle thus derived unite to form a thick muscular mass, 

 from the superficial aspect of which four minute and delicate fleshy slips issue. Each of 

 these ends in a thread-like tendon, and they together constitute a flexor sublimis. The 

 mass of the muscle now gives place to a rope-like tendon which is scooped out superficially 



