192 Annah of the South African Mnneiini. 



The acetabular depression is posteriorly not marked off distinctly 

 from the general iliac surface, and in almost the whole posterior 

 half the surface of the bone is so smooth that it is unlikely to have 

 been covered with cartilage and to have taken any part in the 

 articulation of the femoral head. Most of the anterior half has, 

 however, been covered with cartilage. The greatest breadth of the 

 lower part of the ilium is 205 mm. Above the articular portion the 

 bone becomes constricted and measures only 133 mm. Imme- 

 diately above the narrow portion it widens rapidly to form the iliac 

 crest. As in Bclodon most of the crest lies behind the plane of the 

 acetabulum. It measures in extreme length 280 mm. The anterior 

 portion of the crest is short, rounded externally, and covered with 

 fine grooves radiating from a centre near the supra-acetabular ridge, 

 similar to those seen on the iliac crest of Belodon. The posterior 

 part of the crest is a thick rounded portion which passes backwards 

 155 mm. from the point of articulation with the ischium. Between 

 the anterior and posterior ends the iliac crest is thin and has a 

 slightly convex outline in front and a slightly concave one behind. 

 The only marked differences between this ilium and that of Belodon 

 are that the former is stouter, has the posterior notch considerably 

 deeper, and the articular surfaces for the pubis and ischium very 

 much thicker. In Stagonolejns the ilium differs in having the 

 posterior portion of the crest small. On the inner side of the ilium 

 are two large articular surfaces for the two sacral ribs. The anterior 

 is the larger and is situated opposite the deep depression imme- 

 diately below the supra-acetabular ridge ; the posterior adjoins the 

 anterior and extends out a little distance on the posterior part of the 

 ilium. 



The ischium is a large flattened bone of an almost semicircular 

 shape. The anterior part is much thickened and expanded to form 

 a portion of the acetabulum and to articulate with the ilium. The 

 lower portion of the anterior border is very thin where it articulates 

 with the extra-acetabular portion of the pubis. The thickest part of 

 the acetabular region measures 93 mm. The greater part of the 

 external surface of the ischium is more or less concave. From the 

 acetabular portion a strong ridge runs backwards near the upper 

 edge of the bone ; below this there is a well -marked depression, and 

 from this there spread out well-marked radiating bony fibres. A 

 deep groove extends downwards, backwards, and inwards from the 

 depression, and forms a notch on the lower border of the bone. 

 Otherwise the surfaces are moderately iiat. The breadth behind 

 the acetabulum is 162 mm., and at the broad portion behind the 



