86 The Alligator and Its Allies 



This dorsal end, which forms the ventral side of the 

 acetabulum, is divided into two distinct articular 

 surfaces by a deep, rounded notch; the posterior 

 and larger surface articulates with the ilium, the 

 anterior surface about equally with the pubis and 

 epipubis. 



The pubis (3), which is much the smallest ele- 

 ment of the pelvis, is a small mass of cartilage 

 lying between the ilium above and the ischium 

 below. It forms a small part of the anterior wall 

 of the acetabulum. 



The epipiLhis (4) is a slightly arched bone, some- 

 what enlarged at its proximal end where it unites 

 with the ischium, and flattened out into a fan- 

 shaped extremity, where it is united with its fellow 

 and with the last pair of abdominal ribs by the 

 broad, thin sheet of cartilage or fibrous tissue noted 

 in connection with the abdominal ribs. As men- 

 tioned above, it is called by Wiedersheim and 

 others the pubis. Near the center of the acetabu- 

 lum there is a small foramen. 



The posterior limb (Fig. 29) consists of the usual 

 divisions — thigh, shin, and foot. The femur (f) 

 is a bone of the same general outline as the humerus, 

 though slightly longer and heavier. The head, for 

 articulation with the acetabulum, is rather hemi- 

 elliptical than hemispherical in shape, the long 

 axis of the ellipse being vertical. The distal 

 enlargement is of at least as great, if not greater, 

 bulk than the proximal and shows some indication 



