REPORT ON THE MARSUPIALIA. 11 



In Cuvier and Lanrillard's plates both the short and long slips are figured in the 

 Phalanger (Phalangista cavifrons) (pi. clxxix. fig. 4, q) ; whilst in the Virginian Opossum 

 (pi. clxxv. fig. 4, q) and the Giant Kangaroo the short muscle is alone represented. In the 

 Wombat, Sarcophilus, and Macropus ruficollis, Professor Macalister x describes only the 

 short variety of the muscle, but in the Koala Mr. Young 2 states that the three muscles 

 are present, although the coraco-brachialis medius and coraco-brachialis longus are fused. 

 Biceps. — In the Thylacine the biceps springs by two tendons from the upper margin of 

 the glenoid cavity and from the coracoid process. These after a short independent course 

 unite to form a powerful flattened tendinous band from which the muscular fibres issue. 

 At first the fleshy belly is undivided, but about the junction of the upper with the middle 

 thirds of the upper arm it splits into a superficial and a deep portion (the coraco-radial 

 and the gleno-ulnar muscles). The former is inserted into the radial tubercle, whilst the 

 latter is fixed along with the brachialis anticus into the coronoid process of the ulna. 



In the Cuscus (PI. II. fig. 4, b.) and Phascogale the two portions of the biceps show 

 similar attachments, but the fleshy bellies are distinct throughout, and there is merely a 

 partial fusion of the tendons of origin. If the muscles be forcibly torn asunder in an 

 upward direction it wfll then be seen that, whilst the gleno-ulnar arises from the upper 

 margin of the glenoid cavity alone, the coraco-radial has a double origin, i.e., both a 

 coracoid and a glenoid origin ; it therefore presents the same attachments as the entire 

 muscle in man. 



Brachialis anticus. — In the Thylacinus (PI. I. figs. 4 and 5, b.a.) the brachialis 

 anticus has a linear origin from the posterior aspect of the shaft of the humerus under 

 cover of the outer head of the triceps, but separated from it by a well-marked external 

 intermuscular septum. The muscle winds round the bone so as to clothe its outer surface 

 and gain the anterior aspect of the limb at the elbow-joint ; here it is inserted behind the 

 gleno-ulnar into the coronoid process of the ulna. 



In the Cuscus and Phascogale the brachialis anticus differs from that of the Thyla- 

 cine in deriving fibres of origin from the outer aspect of the humeral shaft, and also in 

 having a closer connection with the external intermuscular septum. 



Triceps. — In Marsupials this muscle is usually very strongly developed, and the three 

 animals under consideration offer in this respect no exception to the general rule. In 

 Thylacinus, indeed, it seems to attain a maximum development. In all the three heads 

 are easily separable. 



In the Thylacine (PI. I. figs. 4 and 5, tr 1 . tr 2 .) the scapular head has a very extensive 

 and at the same time a somewhat peculiar origin. It springs from nearly the whole 

 length of the axdlary border of the scapula and by two distinct sets of fibres, viz., (l) a 

 series which have a tendinous origin from the bone close to the glenoid cavity, and which 

 pass clown to constitute the long head of the triceps as it is usually observed. (2) A 



1 Annals and Magazine of Natural History, vol. v. 5 Journal of Anatomy and Physiology, vol. xvi. 



