OF THE WOMBAT, KOALA, AND PHALANGERS. 



883 



OS calcis deep to that of the mesial part of the muscle. Only a 

 thin membrane connects the two parts. In Phascolarctos the two 

 parts arise as in Phalanger ; at the junction of the proximal and 

 middle thirds of the leg a strong, narrow aponeurosis, which 

 ultimately forms the tendo Achillis, begins to appear on the outer 

 part of the muscle, and the inner part is attached to it. In 



Text-figure 40. 



B. 



Adductor and hamstring muscles oi Phascolarctos cinereus (above), and Fhalanger 



orientalis (below). 

 A.M : adductors; B : biceps ; G.S.N : great sciatic nerve; I. L.L : internal lateral 

 ligament of knee; Q.E : quadriceps extensor; S-M : semi-membranosus ■ 



S-T : semi-tendinosus. 



Pseudochirus the two parts unite, so it resembles that in Phasco- 

 larctos rather than Phalanger. In Phascolomys the inner head 

 arises from the back of the internal condyle, and from a small 

 piece of the popliteal surface of the femur on both mesial and 

 lateral aspects. The outer head arises from the sesamoid bone 

 at the back of the external condyle. Both remain separate for a 

 considerable distance, the mesial pai^t overlapping the lateral one, 



