\',\ WILLIAM A. IIASWELL, M.A., B.SC. 177 



passes over them to the humerus, the part of the muscle between 

 the shoulder-girdle and the arm taking the place of the middle 

 part of the deltoid. In Petaurista there is no fusion between the 

 fibres of the trapezius and those of the clavicular part of the deltoid 

 and none of the fibres of the former muscle are inserted into the 

 clavicle ; whereas in Guscus (1) and to a less extent in Phalaugista 

 the anterior portion of the trapezius actually fuses with the deltoid 

 and some of the fibres of the trapezius are inserted into the clavicle. 

 The arrangement of the humeral part of the trapezius seems to 

 present considerable variations in other families ; it is altogether 

 absent in the Wombat according to Macalister. (2) 



The latissimus dorsi in Petaurista differs from the corresponding 

 muscle in Phalaugista and in Cuscus in being undivided at its 

 insertion ; in the two latter genera it bifurcates to become inserted 

 in two parts — the one part being inserted along with the teres major, 

 and the other into the bicipital groove. 



The humeral offset from the pannicidus carnosus is rather more 

 powerfully developed in Petaurista than in the Phalanger ; 

 in the former it is inserted by a broad thin tendon into the 

 pectoral ridge of the humerus, partly in conjunction with the 

 insertion of the pectoralis quartus, but partly independently. In 

 Phalaugista vulpina the muscle has no independent insertion, its 

 tendon joining that of the pectoralis quartus, and becoming 

 connected also with a tendinous arch between the two insertions 

 of the latissimus dorsi. 



In both Phalaugista and Petaurista, as in Cuscus, the 

 acromio-trachelian consists of two parts arising from the 

 atlas and axis, and diverging to become inserted at a con- 

 siderable distance from one another — the one into the distal part 

 of the spine of the scapula and the proximal part of the acromion, 

 and the other into the vertebral (proximal) part of the spine. 



(1) Cunningham, Reports of the Challenger Expedition, Zoology. 

 Report on the Marsupialia, p. 3. 



(2) " Myology of the Wombat and Tasmanian Devil." Ann. Mag. Nat. 

 Hist., 4th series, Vol. V., p. 159. 



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