14 ANATOMY OF VERTEBRATES. 



the biceps has the usual two origins : the flexor sublimis digitorum 

 is distinct from the flexor profundus in Didelphys. 



The muscles of the hinder extremity are chiefly remarkable in 

 the Kangaroo for their prodigious strength and unusual number : 

 the accessory muscle of the biceps cruris, e. g., arises from a 

 caudal vertebra, and, with that from the ischium, forms two strong 

 fasciculi, one inserted into the outer femoral condyle, the other 

 into fascia covering the gastrocnemii. The pyriformis is also a 

 double muscle. The sartorius has its insertion so modified that 

 it becomes an extensor instead of a flexor of the tibia : it is 

 chiefly fixed to the tibial side of the gristly patella, and by 

 fascia into the capsular ligament of the knee-joint and the 

 anterior proximal tuberosity of the tibia. In a Dasyure (Das. 

 macrurus ) I found that the sartorius had a similar disposition and 

 office. In this ambulatory carnivorous Marsupial the external and 

 middle glutei are so disposed as to extend the thigh, while the in- 

 ternal gluteus inflects and rotates it inward. In a Bandicoot 

 (Perameles lagotis) the sartorius ran nearly parallel with and 

 dermad of the rectus, and was inserted into the upper part of the 

 patella. Besides this sesamoid, which is rarely developed in other 

 Marsupials, I found a thick cartilage attached to its upper part 

 and interposed between the common tendon of the recti and vasti, 

 removing that tendon further from the centre of motion, and in- 

 creasing the power of the extensor muscles of the leg. The rec- 

 tus femoris has its two origins very distinct, and its homotypy 

 with the biceps of the upper extremity is obvious. The gracilis is a 

 very thick and strong muscle. The biceps flexor cruris in the 

 Perameles is a muscle of very great strength ; it terminates in a 

 strong and broad aponeurosis, which extends over the whole 

 anterior part of the tibia, being attached to the rotular tuberosity 

 of that bone, and terminating below in the sheath of the tendo 

 Achillis, whereby this muscle becomes an extensor of the foot. 



All the equipedal Marsupials, whether burrowers as the Wom- 

 bat, climbers as the Koala, Phalangers, and Opossums, or simply 

 gressorial, as the Dasyurida, have the tibia and fibula so connected 

 together as to allow of a certain degree of rotation upon each 

 other, analogous to the pronatory and supinatory movements of 

 the bones of the antibrachium, and the muscles of the leg present 

 corresponding modifications. None of the analogous carnivorous, 

 pedimanous, or rodent Placentals present this condition of the 

 hind leg. In the Kangaroo, the gastrocnemii almost rival those of 

 Man in the bulk of the fleshy part. 



In the Dasyurus macrurus, the plantaris, instead of rising from 



