182 JOTTINGS FROM BIOLOGICAL LABORATORY. SYDNEY UNIVERSITY. 



As in the phalanger the plantaris is intimately united in Petau- 

 rista with the deep surface of the outer head of the gasfrocnemiub ■ 

 In Cuscus it is described by Cunningham as being quite distinct 

 from the latter muscle. In the Koala, according to Macalister, 

 the union is close. 



The tibialis posticus is represented in Petaurista, as in Phalangista 

 and Cuscus ■, by two separate muscles both inserted into the 

 scaphoid. (1) 



As in the forelimb, so also in the hind limb, the flexor muscles 

 of the digits are united in all three genera into one muscular mass. 

 This arises from the posterior surface of the fibula : the superficial 

 part gives origin to tendons passing to the third, fourth and nfth 

 toes ; the deep part supplying tendons for all the digits including 

 the hallux. 



The extensor longus hallucis of the phalanger is described by 

 Macalister as being inserted in the index as well as into the hallux, 

 but this is certainly not the case in the specimens I have examined ; 

 in Petaurista also, as in Cuscus, the insertion is only into the 

 terminal phalanx of the hallux. 



The extensor brevis digitorum, in Phalangista and Cuscus consists, 

 as regards its origin, of a fibular and a pedal part, the former 

 consisting of two slips giving tendons to the fourth and fifth toes, 

 while the pedal part, arising from the calcaneum, ends in delicate 

 tendons for the second and third toes. In Petaurista the pedal 

 part of the muscle is not developed. (2) 



(1) According to Owen (Anat. of Vert. III., 16), the tibialis posticus in 

 Phalangista vidpina- divides into two tendons which are inserted into the 

 internal and middle cuneiforms. 



(2) Owen regards the part of the fibular extensor brevis going to the fifth 

 toe as an internal peroneus. (Anatomy and Physiology of Vertebrates, 

 Vol. III., p. 16.) 



