ART. 15 ANATOMY OF THE EAEED AND EARLESS SEALS HOWELL 39 



form an angle of 63° with the axis of the shaft, thus placing the 

 medial much more distad than the lateral. The reason for this will 

 be discussed on page 127. 



Lower leg: Patella. — The relation of the patella to the femur is 

 discussed in the last paragraph. It is much more conical, especially 

 in the Otariidae, than is the case with most mammals. 



Tibia. — In the Zalophus and Phoca^ respectively, the percentage 

 of the tibia to body length is 22 and 29 (36 in a cat) ; to leg 

 length, 36 and 39; and to the femur, 202 and 200 per cent (104 

 in a cat). The relati^^e proportions of the thigh to the shank are 

 therefore about the same in both animals. In the ZalopJms this bone 

 is relatively straight, robust, and with but slight constriction along 

 the middle of the shaft. In the Phoca it is more curved and there 

 is a greater constriction in the middle of the shaft. In this animal 

 the posterior tibial fossa is deep and much better defined than in 

 the otariid, and the anterior tibial fossa is but slightly indicated 

 in both. In both the articular surface of the head is slightly altered 

 from its normal position, the lateral part being situated a trifle 

 more distad than the medial, this being more accentuated in the 

 otariid. In the phocid there are nodular growths of bone about 

 the border of the head, indicating some sort of pathologic condition. 

 Distad the astragalar articular surface is much deeper and more 

 cupped in the phocid and the medial malleolus does not project 

 beyond the rest of the bone, as it conspicuously does in Zalophus. 

 In the latter the grooves for the passage of tendons are very poorly 

 defined, while in the phocid they are very deep, as they are in the 

 radius. Craniad there is a deep one for the tibialis anticus, and 

 caudo-mediad two, the more medial for the tibialis posticus and 

 the other for the flexor digitorum longus. 



Fibula. — The head of the pinniped fibula is solidly fused with that 

 of the tibia and the distal extremeties of the two bones are immov- 

 ably bound together by ligament. The fibular part of the common 

 head is more or less on a level with the tibial part in the Phoca 

 skeleton, but in the Zalophus it slopes very sharply distad, in this 

 way providing for an excessive degree of flexion of the knee in this 

 animal. That the condition of this detail is not uniform in the 

 Phocidae is, however, shown by a skeleton of Phoca groenlandica, in 

 which there is almost as much of a slope to the fibular head as in my 

 Zolofhus. The relative position of the heads of the two bones is 

 about the same — perhaps a trifle farther caudad in Zalophus — but 

 distad the fibula of the otariid curves quite far craniad, which seems 

 never to be the case in the Phocidae. This changes the position of 

 the ankle joint so that if both animals were normally plantigrade 

 the otariid would toe in to a consfderably greater extent than the 

 phocid. The fibular shaft of the former is almost uniformly cylin- 



