178 JOTTINGS FROM BIOLOGICAL LABORATORY, SYDNEY UNIVERSITY, 



The pectorales muscles in Petaurista have essentially the same 

 arrangement as in Phalangista and in Cuscus. There is a 

 pectoralis major, which consists of a large superficial part itself 

 divisible into two, and a smaller deep part situated beneath it \ a 

 pectoralis minor which lies behind the deep part of the pectoral is 

 major ; and a long pectoralis quartus arising from the linea alba 

 and the fascia over the rectus abdominis. This is an arrangement 

 of the pectoral muscles which seems specially to characterise the 

 present family. 



In all three genera the subclavius is inserted wholly into the 

 clavicle. 



In Petaurista the deltoid consists of two quite separate parts, 

 a scapular and a clavicular, separated from one another by the 

 humeral part of the trapezius. In Phalangista also the two parts 

 of the muscle are distinct, but, as already noticed, the relation of 

 the trapezius to them is a little closer than in Petaurista ; and 

 the same, according to Cunningham, (1) holds of Cuscus. (2) 



In Cuscus there are two coraco-brachiales; in Phalangista and in 

 Petaurista one alone is represented. In the related genus Phasco- 

 larctos (the Koala) there are two distinct coraco-brachiales. (3) 



A s in Cuscus and Phalangista the biceps flexor cubiti consists 

 in Petaurista of two parts separable throughout their length, 

 except near the proximal end ; one of these arises from the upper 

 margin of the glenoid cavity alone, and is inserted into the 

 coronoid process of the ulna, the other has heads of origin both 

 from the coracoid process and the glenoid cavity, and is inserted 

 into the bicipital tubercle of the radius. 



The epitroclileo-anconeus seems to be of universal occurrence in 

 the Marsupialia ; it has the same form and connections in the 

 Petaurista as in Cuscus and Phascogale as described by 

 Cunningham. 



(1) L. c, p. 9. 



(2) The deltoid is described by Macalister as undivided in the Koala 

 ("The Muscular Anatomy of the Koala," Ann. Mag. Nat. Hist. (4), 

 Vol. X., p. 127), but Young (" Myology of the Koala," Journ. Anat. Phys., 

 Vol. XVI., p. 226), describes it as consisting of two distinct parts. 



(3) Young, " Myology of the Koala. 1 ' (Journ. Anat. Phys., Vol. XVI.) 



