244 MR. W. P. PTCEAFT ON THE MORPHOLOGY AND 



for, on removing the biceps cruris, its superficial portion is seen running obliquely 

 upwards and forwards to the whole length of the linea aspera of the femur, from its 

 usual origin. The sciatic artery and nerve are superficial to this muscle (adductor 

 longus of Owen) and parallel to its insertion, as in most birds ; but they, as is not the 

 case except in the Struthiones and Crypturi, perforate it at the ischiadic notch, leaving 

 a small portion of the muscle (the adductor brevis of Owen) above them. The anterior 

 terminal fibres of this muscle are situated external or superficial to the accessory semi- 

 tendinosus. 



" After this muscle has been removed or turned back, there is seen a deeper muscle, 

 which, if the one described above did not exist, would be justly considered to be the 

 femoro-caudal and the accessory femoro-caudal, part springing from the iliac ridge and 

 part from the coccyx, whilst both are inserted into the posterior portion of the linea 

 aspera and have the nerve to the semi-membranosus situated between them and the 

 adductor magnus." This deeper muscle Garrod does not further distinguish. Probably 

 it should be regarded as representing the obturator externus. 



The femoro-caudal, it should be remarked, is very slender; it lies deep of the semi- 

 membranosus. In Garrod's paper he appears to associate it first with the superficial 

 and then with the deeper muscle. 



Mr. Beddard apparently regards the obturator externus of this paper, and the deep 

 layer of muscle described by Garrod, as the muscle which would be justly considered 

 the accessory femoro-caudal, in the absence of the superficial layer just described. 



The muscular mass embracing the emergence of the sciatic nerve and artery 

 should be regarded, I would suggest, as the Struthious adductor referred to by both 

 Garrod and Beddard, but fused distad with the gluteus anterior, and caudad with 

 the accessory femoro-caudal. A comparison of fig. 6, p. 243, will serve to show the 

 probability of the correctness of this interpretation. 



The semitendinosus and its accessory in Casuarius, Dromceus, and Rhea are very 

 similar. In Rhea the former is inserted on to the tibia by means of a long tendon, 

 in the Cassowary at least of the two former genera it loses itself in the gastrocnemius. 

 In Struthio the accessory head is small. In Apteryx, according to Beddard, the 

 accessory head shows a slight variation in its relations within the genus. " In 

 A. australis the accessory head of the semitendinosus was distinctly separated from, 

 though parallel to, the middle head of the gastrocnemius. In A. haasti no such 

 separation is obvious." 



The semimembranosus (ilio-flexorius, Gadow) of Apteryx is two-headed, the second 

 head arising from the ischium ; between these two heads lies the head of the femoro- 

 caudal. 



In Dromceus the semimembranosus, according to Garrod, is peculiar in that it has 

 an aponeurotic connection with the middle of the linea aspera. : .1 



In Casuarius it is but feebly developed ; it passes rapidly into a' thin flat tendon to 



