70 ODOXTORXITHES. 



The post-acetabular part of the ilium is very elongate, and its lower 

 border somewhat curved downward. The free extremity, behind the last 

 coossified vertebra, is thin, and turned slightly upward, and outward. On 

 the lower portion of the outer surface, there is a strong ridge, which arises 

 behind the upper part of the anti-trochanter, and sweeps gently down- 

 ward until it reaches the lower margin of the ilium ; whence it rises 

 gradually, and continues backward to nearly opposite the last sacral 

 vertebra. This ridge is shown in Plate X, figure 1, and its prominence in 

 this specimen (number 1206), may have been somewhat increased by 

 pressure, before removal from the matrix. 



The acetabulum has a well-defined border, which is nearly circular. 

 Above this, there is a large anti-trochanter, or articular surface to which 

 was applied the neck of the feinur. The internal face of the acetabulum 

 was not closed merely by fibrous tissue, as in modern birds, but by bone, 

 which is penetrated by a foramen of moderate size, (Plate XI, figure 1, af). 

 The acetabular region of the ilium is strongly coossified with the sacrum, 

 while nearer its extremities the union is less perfect. 



The Ischium. (Plates X and XL) 



The ischium forms part of the acetabulum, and anti-trochanter, and 

 then, contracting rapidly, is continued backward as a long slender bone, 

 which is entirely free at its distal end. Viewed from the side, the upper 

 margin curves downward, nearly par&llel with the convex ventral margin 

 of the ilium, while the lower border is very gently arcuate, with the 

 convexity below. 



The distal extremity is obtusely pointed, and is somewhat turned 

 upward and outward, terminating nearly opposite the posterior end of the 

 ilium. The anterior half of the free portion is rod-like, and the distal 

 half expands gradually, nearly to the extremity. The outer convex surface 

 of the rod-like portion is continued over the distal half as an obtuse 

 rounded ridge, which extends to the extremity. There are no processes 

 on this bone extending upward toward the ilium, or downward to the pubis. 



