12 ME. ST. GEORGE MIVART ON THE 



The Ilium (figs. 2 & 8, il). 



This bone extends itself over twenty-two vertebrae, namely from the twenty-third to 

 the forty-fifth inclusive. Compared with the same bone in Struthio, its dorsal margin 

 is more convex, its anterior margin more concave (the ventral preaxial angle being more 

 prominent), and the postacetabular part is not so much in excess of the preacetabular 

 portion. It would taper preaxiad but for the ossification (before mentioned) of the 

 ilio-ischiatic ligament which causes it to expand vertically towards its distal end. The 

 gluteal lines do not descend (ventrad) so much as in Struthio ; and the stronger supra- 

 acetabular process comes to jut out more horizontally as VFell as more strongly, making, 

 with its fellow of the opposite side, a flat rhomboidal surface on the dorsum of the 

 ilium. The ilia ai-e flattened against the included postacetabular vertebrae to a 

 remarkable degree. 



The Pubis (fig. 2,])). 



This bone is like what that of Struthio would be if the latter were sharply cut off at 

 the postaxial end of the ischium ; only it is not quite so much bowed outwards. There 

 is, of coui-se, no pubic symphysis. In the young it does not join the ischium distally, 

 but quite resembles the osseous part of the pubis of the young Ostrich when the sym- 

 physial part is all cartilaginous. 



The Ischium (fig. 2, ?'). 



This bone is very slightly, if at all, shorter than the pubis, and ankyloses postaxially 

 both with that bone and with the ilium. It seems to form about the ventral third of 

 the antitrochanteric process. It also slightly ankyloses with the pubis more proximad, 

 so as to cut off the anterior part of the obturator foramen as a separate and much smaller 

 foramen (fig. 2, between Ip & jjs). The two ischia unite together postaxially a little 

 behind the acetabulum, and thence expand transversely as they proceed postaxiad, 

 forming an elongated sheet of bone (concave in both directions on its ventral surface) 

 beneath the sacro-caudal vertebrae. At its distal end it sends down a process, curving at 

 first ventrad and then preaxiad, which ankyloses with the extreme distal end of the 

 pubis. Thus, as it were, the outer ridge of the ischium of Struthio is drawn out, while 

 the surface between the (here relatively approximated) dorsal and ventral ridges coalesces 

 with the corresponding surface of its fellow of the opposite side. 



THE VERTEBRAL RIBS (fig. 1). 



There are nine vertebral ribs, the first and last becoming in the adult (as in Struthio) 

 ankylosed transverse processes. The fourth, fifth, and sixth of these bones unite with 

 sternal ribs. (See fig. 1.) 



The ^rst rib is attached to the fifteenth vertebra, and ankyloses with it in the adult. 

 It is very small, triangular, and very little longer than broad. 



