124 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 7:; 



pubis, and the innominate in this region has corresponding depth 

 to allow for this. These two main movements of the leg — abduction 

 of the thigh and adduction of the shank — are complementary in 

 Phoca, for as the plantar surface of one foot is pressed against that 

 of the other during active swimming, adduction of the right femur, 

 for instance, assists abduction of the left shank, and the opposite. 



The only other details of the innominate that merit mention con- 

 sist of the dorsal spine or tuberosity of the ischium in the Phocidae 

 extending well dorsad and developed by the narrow and somewhai: 

 tendinous origin of the superficial biceps femoris, which in the Ota- 

 riidae does not arise from the innominate. Another detail is the ten- 

 dency in the Phoca toAvard obliteration of the femoral process, and 

 the development in this animal of a distinct and large process upon 

 the ventral border of the ilium for the insertion of the psoas magnus. 

 of such importance in its swimming. 



Length of limb, comprising the sum of femur, tibia, and the dis- 

 tance from the tip of the second toe to the posterior border of the 

 astragalar condyle, is without much significance in the Pinnipedia 

 because so much of the limb is within the body. However, as com- 

 pared to bod}'' length this item is 104 per cent in the cat. 62 in Za^o- 

 ■phus, and 74 in Phoca. 



The femur in this order has become very short indeed. Whereas 

 this bone in the cat is 35 per cent of the body length, in the Zalophus 

 it is but 22 and the Phoca 29 per cent. In function it plays a ver}' 

 minor part as a segment of the limb and I regard its diminution in 

 size as intimately correlated with the shortening of the ilium anil 

 consequent reduction in the length of the muscles between these two 

 points as well as by the great reduction in femoral mobility. I am 

 not prepared to say that the position of the femur is uniform in the 

 Otariidae, but at least in the Zalopus dissected the static position 

 of this bone was apparently at a cranio-lateral inclination forming 

 an angle with the body axis of about 45°, but markedly rotated. In 

 other words, the femur is normally carried very strongly flexed and 

 lotated cranio-mediad. (See fig. 30.) In contrast to this the femur 

 of the Phoca was directed a trifle caudad of laterad to the body axis 

 and there was no marked rotation. As a result of these postures the 

 muscles that pull cranio-mediad (the gluteal complex) upon the 

 greater trochanter of the otariid chiefly rotate the femur, with the 

 final result on land of turning the toes outward. This same action m 

 the Phoca results in the abduction and extension of the femur. 

 Another result of these femoral positions is that in reality the effective 

 length of the otariid leg is less than the sum of the tibia and pes, 

 while in the phocid it is greater. The arc of effective flexion and 

 extension of the femur seems to be only about 25° in Zalophus and 

 30° in Phoca^ with the amount of flexion in the former slightly greater 



