Vol. 56.] 



ARISTODESMUS RUriMEYTERI. 



635 



The Pelvis. 



The pelvic basin is formed by the pubis and ischium, of which 

 only the inner or visceral surface is seen. The bones of the left 

 side are in sutural union throughout their length, but the form of 

 the anterior margin of the pubis is not evident, nor is the whole 

 shown of the pubic part of the acetabular border. The absence of 

 an obturator- foramen between the pubis and ischium is a character 

 shared with Pareiasaurus and Procolophon ; a median sutural union 

 occurs in the Cetiosauria, but the forms of the bones are dissimilar. 



{a) The Ilium. (Fig. 6, p. 638.) 



The right ilium was almost vertical, being very slightly inclined 

 forward. The bone is moderately deep, from the superior slightly 

 convex margin of the iliac crest to the middle of the iuferior angle 

 of the acetabulum, which was imperforate, in the way that has been 

 described in various South African Anoniodonts. The bone is convex 

 from above downward. Its anterior and posterior margins are 

 reflected outward, so that the blade of the bone, which is ;9 inch 

 wide, is concave from side to side, and convex from above downward. 

 The blade is very slightly expanded from front to back. 



Fig. 5. 



Visceral surface of pubis and ischium in Aristodesmus 

 Kiitimeyeri. (Nat. size.) 



? Pubis displaced. 



Pubis, 



Ischium 



(b) The Ischium. (Fig. 5.) 



The right and left ischia were inclined together, and united by 

 a median sutural surface, so as to form with the pubic bones a 

 broad basin of moderate depth. The ischium has a subquadrate 

 aspect, owing to the straight transverse suture, which separates it 



