]Q6 THE VOYAGE OF H.M.S. CHALLENGER. 



In a large specimen of Ardoccphalus gazella this muscle could probably be divided into two. 

 It arises from the outer hindward ventral half of the pubic bar, behind the obturator foramen, from 

 all the surface between the origins of the obturator externus, and the gracilis and adductor niagnus, 

 and from the hindward quarter of the ischial bar to the origin of the quadratus femoris. It is 

 inserted obliquely across the back surface of the femur, from the lower end of the great trochanter 

 to the middle of the inner surface of the shaft of the femur, ending at the junction of the 

 anterior surface with the inner. The adductor longus primus and secundus of Otaria form the 

 adductor longus of Ardoccphalus. In Trichcchus the adductor longus has only one head. It 

 adducts the thigh in Macrorhinus, but in Ardoccphalus besides adducting, the fibres upon the 

 posterior surface rotate it outwards, those on the inner surface inwards. 



From the lower end of the great trochanter in Ardoccphalus, crossing the back of the femur, and 

 terminating at the middle of the junction of the posterior with the inner surface, is a ridge of bone 

 resembling the linea aspera of human anatomy and giving attachment throughout its entire length 

 to the adductor longus. This is a faint ridge in Macrorhinus, but it lies midway between the 

 upper and lower ends of the great trochanter, and terminates in the middle of the back of the shaft 

 at the junction of the upper third and lower two-thirds of the femur, the pectineus touching it. 

 In Ehoca grcenlandica there is a similar ridge to the last, but it ends at the middle of the inner 

 border of the femur ; the pectineus also lies above and on it. Humphry describes the adductors in 

 a general way. The name as he uses it is not altogether unsuitable, for the muscles have this action. 

 His adductor magnus I take to be the semimembranosus. Of his other two adductors, one is the 

 pectineus and the other probably the ilio-fenioralis. 



The Adductor brevis in Macrorhinus leoninus. If the pubic bar be divided into fourths, the 



adductor brevis arises from the second fourth behind the pectineal muscle, near the ilio-pectineal 



eminence outside the brim of the pelvis, and slightly from the outer surface dorsal to this. It passes 



upwards and outwards, and is inserted into the middle of the posterior surface of the femur, outside 



the insertion of the pectineus. The exact spot is found by drawing a line from the lower end of the 



great trochanter, across the back of the femur, when the middle of this line is the insertion surface. 



In Arctocephalus gazella it arises from the pubic bar outside the brim, and from the ventral 



half of it behind the origin of the pectineus. It lies between the adductor longus and the pectineal 



muscles. It is inserted obliquely across the posterior surface of the femur, from the lower end of 



the great trochanter to the insertion of the pectineus behind the small trochanter, and higher 



than the longus which is upon the linea aspera. Murie describes this muscle as a primus and 



secundus, but I think the primus is the pectineus and the secundus the above-mentioned muscle. 



What he gives as the pectineus is inserted into the internal condyle of the femur, and the primus 



below the neck and trochanteric fossa, which is the usual insertion of the pectineus. It rotates 



outwards and flexes the thigh. 



The Adductor magnus is called primus and secundus by Murie and is only found in Ardoccphcdus 

 gazella. It arises from the outer rim of the innominate bone, dorsal to the symphysis, extending 

 to the commencement of the dorsal border of the ischial bar. It passes forwards and outwards 

 from the pelvis to the knee, and is inserted into the lower half of the shaft of the femur at the 

 junction of the inner with the front surface, across the internal condyle, into the tibia immediately 

 behind it, and into the capsule of the knee-joint on the inner side. It adducts both the femur and 

 the tibia. It is a single muscle in Trichcchus. 



