10 MR. ST. GEORGE MIVART ON THE 
against the ilium, though the neural arch and spine are quite rudimentary. At a more 
advanced stage (as seen in No. 1057*) all that remains in an osseous condition is a long 
and narrow body with a pair of transverse processes of very cancellous texture. Post- 
axial to this vertebra the vertebre become atrophied in the adult to such a degree that 
merely a long narrow osseous band, of very cancellous structure, represents the bodies, 
(from that of the thirty-seventh to the forty-fourth inclusive) of the vertebre ; and these 
have diverging parapophysial processes of similar unsubstantial texture. 
The thirty-seventh, -eighth, and -ninth vertebre are elongated vertebra enclosed between 
the posterior parts of the ilia. Behind these and above the ischia are four (in No. 1057), 
or five (in Nos. 1361 & 1361 F) vertebra, which gradually become less imperfect as we 
proceed postaxially—the bodies broadening out and the neural spines getting shorter, 
thicker, and more stumpy,—the ultimate vertebrae more or less ankylosing with the 
ischia. 
THE CAUDAL VERTEBR2. 
The forty-fifth, -sixth, -seventh, -eighth, -ninth, and fiftieth vertebre.—Postaxial to the 
ischia are six vertebree, which gradually diminish postaxially. None have transverse 
processes. ‘The first three, sometimes the first five, have more and more minute neural 
arches. The last vertebra is grooved dorsally; and sometimes the last three are so 
grooved. 
The last apparent vertebra, the pygostyle, is not dorso-ventrally expanded into an 
osseous plate, as it is in Struthio, but is cylindrical and short, not being twice the 
length of the vertebra preceding it (fig. 2). It looks as if made up of only two 
vertebre ankylosed together. 
THE PELVIS. 
In the adult the pelvis consists of twenty vertebrae and two ossa innominata. 
When viewed preazially, its aspect differs greatly from that presented by the pelvis 
of Struthio, on account of the absence of the descending pubes and pubic symphysis, in 
Rhea, as also because the ischia curve inwards, converge, and unite together just post- 
axiad to (and, of course, on the ventral side of) the acetabula, and thence contiuue 
onwards, so united, postaxiad. The iliac roof of the first pelvic vertebra is much more 
concave on each side than in Struthio. ‘The ilium also sends out a sharper process 
(the supratrochanteric process) above each trochanteric process (fig. 2, st). 
When viewed postaxially, the same absence of a pubic symphysis and the presence of 
an ischiatic one produces a very great difference of aspect from this point of view also. 
Again, the summit of the pentagonal mass is horizontal, owing to the crest of the ilium 
not rising dorsally as much as in Struthio. 
Viewed laterally, the part which was, in the description of the pelvis of Struthio, 
1 In the Museum of the College of Surgeons. 
