128 AMERICAN PERMIAN VERTEBRATES 



tracting into a rather narrow neck just above the acetabulum, with 

 a rather deep notch posteriorly, the antero-posterior extent of 

 the bone below being not quite as great as that above. The ante- 

 rior border is thicker and much more extensive, the deepest part 

 being about midway between the pubic symphysis and the superior 

 angle. The posterior border is U-shaped, with nearly equal arms. 

 On the inner side the lower part is convex antero-posteriorly. The 

 sacral ribs doubtless were attached at their extremities by ligaments 

 extending the full length of the bone above. The pubes and ischia 

 are not very different in shape, and of about equal size. The pubis 

 has a thin anterior margin in front of the acetabulum with a dis- 

 tinct pectineal process near the acetabular margin. In articula- 

 tion the two pubes leave a deep V-shaped emargination, the thick- 

 ened symphysial margin confined to the posterior part of the inner 

 border. The obturator foramen pierces the bone obliquely, its 

 external orifice just within the acetabular margin on the posterior 

 two-fifths of the bone. The ischium has a thin, convex posterior 

 margin, the two bones in symphysis showing only a small V-shaped 

 exmedian excision. The thickened symphysial margin is formed in 

 nearly equal parts by the three bones, that of the ilium the greater. 

 The ilium has an overhanging process above. The pubo-ischiadic 

 suture passes directly inward at the middle of the inferior margin 

 of the acetabulum and divides the horizontal part of the pelvis 

 into nearly equal parts. 



Femur (Plate XXII, Figs. 1-4). — The femur is relatively short 

 in comparison with that of Varanosaurus, but somewhat stouter. 

 The head is broad from side to side above, thinned at the outer 

 posterior angle. The digital fossa is shallow but broad. The 

 trochanter is prominent, directed backward and a little inward. 

 The shaft of the bone in the middle is rather slender and prismatic 

 in shape. The fibular condyle as usual is much deeper antero- 

 posteriorly than the tibial, and the latter is placed at a sharp angle. 



Tibia (Plate XXII, Figs. 5, 6). — The tibia is short and thickset, 

 rather slender in the middle, much expanded at either extremity, 

 the inner border gently, the outer border deeply, concave. The 

 lower extremity is expanded somewhat obliquely backward and 

 inward, has its articular surface broadly oval, its long diameter a 



