AB1-. 15 ANATOMY OF THE EARED AND EARLESS SEALS HOWELL 125 



than extension. Abduction and adduction is greater — possibly 

 rlirough as much as 40°. 



The flatness of the pinniped femur is probably attributable to a 

 variety of stimuli — the lack of need for antero-posterior thickness, 

 the need for a greater trochanter extending well laterad of the 



I 



Fig. 30. — Di.^gram illustrating approximate static posture (solid lines) and 

 dbghee of possible movement (broken lines) in life of each jointed seg- 

 MENT OF THE POSTERIOR LIMBS OF ZALOLPHDS (Z) AND PHOCA HISPIDA (P). /, 

 INNOMINATE; T, THIGH; S, SHANK; H, HEEL (ASTOAGALUS AND CALCANEUM) ; AND 

 F, REMAINDER OF FOOT 



acetabulum and for a broad distal extremity. The greater tro- 

 chanter of both animals is very similar. In the Zalophus the tro- 

 chanteric fossa is a slight concavity while in Phoca it is a very deep 

 pit because in this animal the muscles inserting in its vicinity are 

 more specialized in order that all may perform practically the same 

 act and their insertions are more circumscribed and more strictly 



