50 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. XIV. 



of this muscle are essentially as in Didelphis and different from those of 

 most other marsupials, in which the so-called crurococcygeus is not so 

 well developed, although tendinous intersections have been found in 

 Thylacinus, Dasyurus, and Trichosurus (fide Thompson and Hillier, 

 1905, p. 316) and in Chceropus (Parsons, 1903, p. 73). 



Gracilis. Origin from the pubic symphysis and the ascending ramus 

 of the ischium nearly half way to the tuberosity. Anteriorly a few fibers 

 reach to the base of the marsupial bone. Insertion aponeurotic on the 

 inner surface of the distal half of the proximal third of the tibia. 



Semimembranosus. Origin fleshy from the outer side of the ascend- 

 ing ramus of the ischium, occupying the middle two-thirds of the space 

 between the symphysis and the tuberosity. Insertion by a broad ten- 

 don on the inner side of the head of the tibia entad of the internal lateral 

 ligament of the knee joint which is strongly developed. A large thick 

 muscle elliptical in cross section. No -presemimembranosus was dis- 

 tinguished, but it may be represented in the somewhat anomalous 

 muscle here called caudofemoraUs although that has no ischial origin. 



Sartorius. Origin on the dorsal border of Poupart's ligament. 

 Insertion in the fascia extending from the knee joint and the patella to 

 the proximal third of the front edge of the tibia. It is a thin band con- 

 sisting of one layer of muscle fibers only and can scarcely be functional. 

 This muscular part is clearly differentiated from the fascia on either side 

 of it which cover a great part of the inside of the leg immediately be- 

 neath (entad) the mass of fat. Between the sartorius and the next layer 

 of muscle is the crural nerve and its branches, of which the saphenus 

 innervates the sartorius and runs down the side of the leg (PI. VI, fig. 2). 

 It is practically imbedded in the sartorius at this point and is visible 

 through the thin muscle layer. The insertion of the muscle is ectad of 

 the gracilis. 



This much-reduced, almost rudimentary muscle, is easily over- 

 looked and it was at first thought that a sartorius was entirely absent or 

 fused with the gluteus maximus. It was possible also that it might be a 

 second gracilis. It has been demonstrated in two specimens, however, 

 and its relations with the saphenus nerve seem to justify the conclusion 

 that it is in reality the sartorius. Its origin from Poupart's ligament is 

 paralleled in certain edentates, as sloths and armadillos. A partial 

 origin from Poupart's ligament has been noted in Sarcophilus by 

 Macalister (1870, p. 170). In the Insectivora, although usually absent, 

 the sartorius is found in Gymnura partly attached to the gracilis. 



Gastrocnemius. The medial head arises by a short thick tendon from 

 the inner transverse surface of the inner condyle of the femur and the 

 intercondyloid notch just distad of the caudofemoraUs and the adductor 



