REPORT ON THE MARSUPIALIA. 39 



and the two first pieces of the sacrum, and it is inserted into the upper part of the small 

 trochanter independently of the Uiacus. 



The iliacus springs from the lower border and iliac fossa of the ilium, and blending 

 with the fibres of the psoas magnus it is inserted into the small trochanter and the 

 surface of the femoral shaft immediately below this. 



Gracilis. — This is a powerful broad muscular band which springs from the side of 

 the pubic symphysis. This origin extends as high up as the antero-inferior angle of the 

 marsupial bone, but in neither animal was the muscle in any way attached to this bone, 

 as is the case in the majority of Marsupials. Indeed, Macalister : states that in every 

 Marsupial that he has examined he has noticed an attachment of the gracilis to the 

 marsupial bone. Young, 2 however, does not mention it in the Koala. In the Cuscus 

 the gracilis (PI. III. fig. 2, g.) has an extensive insertion into the anterior sharp ridge of 

 the tibia in its middle third ; in the Thylacine it presents a much more limited insertion 

 into the subcutaneous surface of the tibia, a short distance below the internal tuberosity 

 (PL IV. fig. 1, g.). 



Pectineus. — In the Cuscus this muscle is more strongly marked than in the 

 Thylacine. It presents in the former a small pointed origin from the anterior margin of 

 the pubic bone, and also slightly from the outer and lower angle of the large marsupial 

 bone. In the Thylacine it springs entirely from the cartilaginous nodule (PL III. fig. 1), 

 that represents the marsupial bone, and is inserted into the femur, immediately below 

 the small trochanter. In the Cuscus it expands, and has a linear insertion into the middle 

 third of the posterior aspect of the shaft of the femur in front of the adductor brevis. 



Triceps adductor. — In the Tliybtciue this muscular mass is divided as in man into 

 three strata, but the ordinary terminology does not express the relative characters of 

 these three strata ; thus the adductor longus is the shortest muscle, the adductor brevis 

 the bulkiest, and the adductor magnus the longest. 



The adductor longus is very similar to the same muscle in man. It has a pointed 

 origin from the base of the marsupial bone, and it expands as it passes downwards 

 to be inserted into the middle third of the posterior aspect of the femur, where it 

 is fused with the subjacent adductor brevis. The adductor brevis (PI. IV. fig. 1, a.b.) 

 has a wide origin from the pubic arch, and the anterior part of the ischial tuber- 

 osity. It is with difficulty separated from the adductor magnus, and it is inserted 

 into the posterior aspect of the femur from the small trochanter above to the internal 

 condyle below. Towards its lower part it is perforated by the femoral artery, as it 

 passes backwards to enter the popliteal space. The adductor magnus (PI. IV. fig. 1, a.m.) 

 arises from the tuber ischii, under cover of the semi-membranosus and gracdis. It is not 

 so bulky as the adductor brevis, and is inserted into the lower two-thirds of the posterior 

 aspect of the shaft of the femur, and also by fleshy fibres into the inner aspect of the 



1 Ann. and Mag. Nat Hist., vol. v., 4th ser. 2 Journal of Anatomy and Physiology, vol. xvi. 



