108 Prof. H. G. Seeley 07i the 



Ilium, (Fig. 4.) 



The form of the ilium (fig. 4) is, so far as I am aware at 

 present, without close parallel in any carnivorous member 

 of the same group. 



Pubic articulation. 



Ischiac articulation. i 



Acetabular arch. 



Left ilium, inner lateral aspect. ^ nat. size. No. 358. 



The bone is subtriangular, with a long, superior, slightly 

 convex iliac crest, which terminates in a small preacetabular 

 process and a larger postacetabular process. The length of 

 the crest is 9 inches ; it is gently curved from front to back, 

 so that there is a slight reflexion outward of the extremities 

 of the bone. Assuming that the sacral vertebra and ilium 

 belong to the same animal or animals of similar size, this 

 length would indicate that there were not fewer than three or 

 more than four vertebraj in the sacrum. The vertical height 

 from the articular surface of the acetabulum in front is 

 3| inches, and the corresponding height from behind is 

 6 inches, so that in general configuration the form of the ilium 

 approaches most nearly to Aetosaurus ferratus (Fraas) ; but 

 the preacetabular process is less developed, as are the 

 descending processes of the ilium for the pubis and ischium. 

 The acetabular arch between the limits of the ischium and 

 pubis is 3^ inches long ; it is 2 inches wide in front and 

 1^ inch wide behind. The surface is divided into two por- 

 tions, an external and an inner : the external portion is 

 convex from the outer margin inward and increases in 

 width as it extends posteriorly; the inner portion is some- 

 what shorter and concave in width as well as in length. 



I suppose the superior crest to have been more or less 

 parallel to the vertebral axis, so that the thickened rounded 

 posterior angle of the ilium was thrown downward and did 

 the major work of supporting the femur. The ischiac suture 

 is slightly worn ; it is about 1 ^q inch wide and 1 inch long 



