22 MR. ST. GEORGE 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 vertebre are not raised up above the aceta- 
bulum as they are in Rhea. 
THE SACRO-CAUDAL VERTEBR/. 
These vertebre, which are those from the thirty-eighth to the forty-seventh (or 
forty-eighth) inclusive, differ much from those of Rhea by their more substantial 
ossification. From Struthio’s vertebre (thirty-ninth to forty-sixth) they differ in that 
their transverse processes are more like the transverse processes of the sacral vertebre. 
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 vertebrae are well ankylosed; and their spines be- 
come rapidly shorter as we proceed postaxially. They never ankylose with the ischia. 
THE CAUDAL VERTEBRZ. 
The caudal vertebra (that is to say, those from the forty-cighth to the jfifty-fifth 
inclusive) differ greatly from those of hea, 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 pygostyle 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 vertebre ankylosed together. 
THE PELVIS. 
In the adult the pelvis consists of twenty-one or twenty-two vertebre, as well as of 
the ossa innominata, 
Viewed preavially and postaaially 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 /aterally 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 
