876 DR. CJ. F. SONNTAG ON THE MYOLOGY 



outer sixth of the clavicle, the upper border of the acromion, and 

 the spine of the scapula. I believe the extent of this muscle is 

 partly due to varying degrees of functional activity. 



Deltoid (text-fig. 39 A-C) : — In Phascolomys the origin forms a 

 continuous line along the whole length of the clavicle, the 

 acromion and lateral third of the spine of the scapula. The 

 clavicular fibres receive the trapezius, and the acromial fibres and 

 trapezius form a powerful cephalo-humeralis. The clavicular 

 deltoid also fuses with the superficial part of the pectoralis major, 

 and the two are inserted into the pectoral crest. From the 

 scapular fibres a long, narrow, strap-like band I'uns to the deep 

 fascia over the radial border and dorsum of the forearm and 

 carpus. In Phascolarctos the muscle is also entire, the clavicular 

 origin is not so extensive, and the narrow band given off fuses 

 with the supinator longus. In Phalanger and Fseudochirus the 

 clavicular origin is not as extensive as in Phascolomys, the 

 clavicular and acromial parts are separate, and no slip is given off 

 to the forearm. 



Scapular Muscles (text-figs. 36-38) : — I agree with Macalister 

 (18) that the supraspinatus is larger than the infraspinatus in 

 Phascolomys and the Phalangers, but I observed the reverse in 

 Phascolarctos. Young (14) states that the infraspinatus is slightly 

 larger than the supra,spinatus. The subscapularis and teres major 

 are essentially similar in all, and there is a cei-tain amount of 

 fusion between the latter and the latissimus dorsi and doi-so- 

 epitrochlearis. The teres minor is fascial in Phascolomys, thin 

 and with a tendinous attachment to the scapula in Phascola7'ctos, 

 and thin and muscular in Phalanger and Pseudochirus. Even 

 when it is muscular there is a considerable degree of fusion with 

 the infraspinatus. Meckel (6) states that the absence of a teres 

 minor as a distinct muscle appears to be general amongst 

 marsupials. 



The characters of the Coraco-brachialis in many forms, including 

 the animals described in this paper, have already been recorded, 

 and Cunningham (2) has collected the observations. My own 

 observations do not diflfer from his. 



Biceps : — The two heads of origin are in contact, but not fused, 

 in Pseudochirus, and the two bellies (gleno-ulnar and coraco- 

 radial) are fused from the middle of the arm onwards. In the 

 distal portion of the arm the two parts separate again and run to 

 the radial tuberosity and coronoid. In Phalanger the tendons of 

 origin are fused to form a tendinous sheet. The muscle bellies 

 remain fused to the distal part of the arm where the stout radial 

 and slender ulnar components are given off. In Phascolomys and 

 Phascolarctos the origins are conjoined, but the bellies separate 

 sooner from one another in the latter. 



Brachialis Anticus : — In all forms it arises on the outer 

 surface of the shaft of the humei^us, and winds round it to be 

 inserted into the ulna with, or deep to, the gleno-ulnar component 

 of the biceps. In Phascolarctos it is fused with the biceps, but 



