8 4 
Annals of the Transvaal Museum 
terior process, a long and slender preacetabular process and a short, thick 
postacetabular process. The upper portion of the ileum is very thin, the lower 
portion is thicker. The upper border is convex. The spina iliaca anterior 
terminates in a sharp point, while the spina posterior is broad and its end 
truncated. There is a low ridge on the medial surface of the hinder end of 
the ileum. This ridge starts behind the middle of the bone and is continued 
on to the spina posterior. It is situated very near to the lower border of the 
spina and is practically parallel with it. The hinder border between the spina 
posterior and the processus postacetabularis is straight. The length of this 
straight border is 21 mm. The open acetabulum cuts into the ileum to a depth 
of 17 mm. and a breadth of 41 mm. Above the acetabulum the medial surface 
of the ileum shows a deep fold, that is to say, here the lower portion of the 
ileum is bent inwards on the upper portion. This groove corresponds with the 
crista supraacetabularis on the lateral surface. 4 The medial surface between 
this groove and the acetabular border is convex. The articulation surface may 
therefore be concave. Groove and acetabular border are nearest to each other 
at the root of the processus praeacetabularis. From this point border and 
Fig. 3. Aristosaurus erectus. Medial view of the left ileum. About nat. size. 
groove diverge backwards. From the position of the groove one would con- 
clude that the acetabular surface extends from the crista supraacetabularis 
inwards and very much downwards and therefore also forms a lateral articu- 
lation surface. 
The processus praeacetabularis is slightly narrower near its junction with 
the body of the bone than near its extremity. It reaches much further for- 
wards than the spina anterior. Between the two there is a deep and wide 
notch. The length of the processus praeacetabularis, measured from the base 
of this notch, is 36 mm. The distance between the end of the spina iliaca 
anterior and that of the spina iliaca posterior is 75 mm. The height of the 
ileum, measured from the lower end of the processus postacetabularis to the 
upper border, is 46 mm. 
Pubis. 
The pubes are beautifully preserved. The right pubis is complete, except 
for its lateral distal corner, of which, however, the impression is present. The 
left pubis is broken in two, the proximal half being in one slab and the distal 
half in the other. There is no indication that the pubes were fused together 
medially. This does not exclude the possibility that they were actually fused, 
because of the medial borders of both bones only a very small portion of that 
of the right pubis is preserved. 
