22 ME. ST. GEORaE MIVART ON THE 



cesses are almost subequal in size ; but the most postaxial is axially broadest. There is 

 hardly a trace of a median keel. These vertebrse are not raised up above the aceta- 

 bulum as they are in Rhea. 



THE SACRO-CAUDAL VERTEBRA. 



These vertebrse, which are those from the thirfy-eighth to the forty-seventh (or 

 forty-eighth) inclusive, differ much from those of Rhea by their more substantial 

 ossification. From Struthio's vertebrse (thirty-ninth to forty-sixth) they differ in that 

 their transverse processes are more like the transverse processes of the sacral vertebrse. 

 Thus, when the pelvis is viewed ventrally, there is no break behind the sacral transverse 

 processes ; but the openings between the transverse processes become smaller and more 

 distant postaxiad, owing to the gradually increasing axial breadth of the successive trans- 

 verse processes. The bodies of these vertebrse are well ankylosed ; and their spines be- 

 come rapidly shorter as we proceed postaxially. They never ankylose with the ischia. 



THE CAUDAL VERTEBRA. 



The caudal vertebrse (that is to say, those from the forty-eighth to the fifty-fifth 

 inclusive) differ greatly from those of Rhea, and even exceed those of Struthio, in the 

 development of their transverse processes, which project outwards and postaxiad. 

 Their development, however, is irregular both as regards size and direction. Each 

 neural spine is flattened dorsally, and vertically grooved postaxially. The first and, 

 sometimes, also the next two caudals have strongly projecting postzygapophyses, which, 

 however, do not attain the vertebra towards which they tend. 



The fygostyle is irregular and subcylindrical, and very unlike that of Struthio. It is 

 about twice the length of the vertebra preceding it, and looks like three small and 

 diminishing vertebrse ankylosed together. 



THE PELVIS. 



In the adult the pelvis consists of twenty-one or twenty-two vertebrse, as well as of 

 the ossa innominata. 



Viewed preaxiaUy and postaxially it differs from the pelvis of Rhea in the non-union 

 medianly of the ischia, and the non-descent of the postaxial part of the ilium, as also 

 in the less concavity between the supra- and antitrochanteric processes. 



When viewed laterally the whole ilium is more convex dorsally than in Rhea, and the 

 postacetabular part of the ilium more so than even in Struthio. The ischium and ilium 

 almost join at their distal ends postaxially. The supratrochanteric process is very 

 slightly postaxiad to the antitrochanteric one. The acetabular opening is much smaller 



