36 THE VOYAGE OF H.M.S. CHALLENGER. 



fascia on the outer aspect of the leg from the external condyle of the femur in front to 

 the external maleolus behind. It has no femoral head of origin, so that the name 

 biceps is in this respect inappropriate. 



The caudal portion (PI. III. fig. 1, c.t.) of the muscle has not been noticed in any 

 Marsupial so far as I am aware. 1 It is a long ribbon-shaped muscle, which arises in the 

 gluteal region from the transverse processes of the first and second caudal vertebrae: in the 

 same plane as the gluteus medius, and under cover of the agitator caudse. From this 

 origin it proceeds downwards in the interval between the ischial tuberosity, and the great 

 trochanter superficial to the biceps proper. The bicipiti accessorius of Haughton lies under 

 cover of the biceps. Reaching a point opposite the posterior aspect of the knee-joint, it 

 gives a small muscular slip to the semi-tendinosus (PI III. fig. 1, s.t., and fig. 2, s.), and 

 splits into two divisions, which diverge from each other so as to embrace the posterior 

 aspect of the leg. The fibular division fuses with the posterior margin of the biceps 

 proper, and is inserted with it into the fascia on the outer aspect of the leg ; the tibial 

 portion, which is the longer of the two, ends in an aponeurotic expansion which is 

 inserted (PL III. fig. 2, c.t.) into the inner subcutaneous surface of the tibia about its 

 middle, at a lower level than the insertion of the semi-tendinosus (PL III. 2, s.t.), and 

 slightly overlapped by the gracilis (PL III. fig. 2, g.). 



In Thylacinus the biceps muscle is very complicated. It consists essentially of three 

 portions — (1) a biceps proper, (2) a superficial caudal portion, and (3) a deep caudal part. 

 These three subdivisions are brought into close association with each other by numerous 

 fleshy slips which pass from the one to the other. 



The biceps proper (PL IV. fig. 5, b.) is more massive than in Cuscus, and not nearly 

 so expanded at its insertion ; indeed, it is merely inserted into the fascia over the outer 

 aspect of the knee and upper third of the leg. 



The superficial caudal division (PL IV. figs. 1 and 5, b~.) of the muscle is the repre- 

 sentative of the caudal part of the biceps in the Cuscus. It arises from the transverse 

 processes of the second and third caudal vertebras, and passing downwards upon the 

 origin of the biceps proper it gives a slip to the semi-tendinosus (s.t.), and then divides 

 into a tibial and fibular part. The tibial portion (PL IV. fig. 1, b 3 .) is the larger of the 

 two, and being reinforced by a slip from the semi-tendinosus it proceeds downwards along 

 with this muscle to the inner aspect of the leg, where it is inserted into the tibia about 

 the middle of its inner subcutaneous surface. The fibular part (PL IV. fig. 5, b 2 .) is 

 reinforced by a long slender slip from the biceps proper, and is inserted into the fascia 

 on the outer aspect of the leg, behind and in conjunction with the biceps proper. 



The deep caudal portion (PL IV. fig. 5, b 1 .) of the biceps muscle represents the bicipiti 

 accessorius of Haughton. It is a long narrow slip which springs from the transverse 



1 It appears to be figured by Cuvier and Laurillard in the Kangaroo Rat and in the Opossum (pi. clxxx. r 1 and 



pi. clxxiv. r'). 



