AXIAL SKELETON OF THE STRUTHIONIDA, 2 
foramina are placed between this vertebra and its successor. The diapophysis has 
aborted or has*become fused with the neural spine. 
The twenty-eighth vertebra (fig. 9, 5) seems to answer to the thirty-second vertebra of 
Struthio, but is not concave either ventrally or laterally. Iam unable to say whether 
its neural arch is deplaced or not. There is no diapophysis; and the parapophysis may 
be absent, or it may (as in No. 1361 z) be present as a process abutting against the 
preacetabular process of the ilium, like the parapophysial process of the twenty-seventh 
vertebra, but considerably smalJler than the latter in all its proportions. 
The vertebra from the twenty-ninth to the thirty-second inclusive’ are devoid of trans- 
verse processes, but have a pair of superimposed neural foramina at the postaxial ends 
of their neural arches. A median hypapophysial keel extends postaxially, beginning 
beneath the thirtieth vertebra. The last (thirty-second) vertebra may send a thin para- 
pophysial lamella to abut against the ilium, and so resemble the vertebre of the next 
category. These vertebrae without transverse processes might be distinguished as 
Lumspo-SacRAL VERTEBR&, a category not present in Struthio, in which genus these 
yertebre have parapophyses, as have also the more postaxial lumbar vertebre. 
THE SACRAL VERTEBR. 
The thirty-third vertebra.—This is the first vertebra which normally develops a 
transverse process (fig. 8, ¢), abutting against the postacetabular (or rather, here, swpra- 
acetabular) part of the ilium. This transverse process seems, in the young, rather 
diapophysial than parapophysial in its nature; but with age the plate descends to a 
lower level. There is a strong median subvertebral keel. 
The thirty-fourth vertebra. In this vertebra the parapophysis becomes more conspi- 
cuous (fig. 8, p). In the young it is seen to form (as in S¢ruthio) in conjunction with 
the diapophysis (d) a flattened surface for the ilium. The vertebra is generally smaller 
than is its serial predecessor ; but the median subvertebral keel is well developed. 
The thirty-fifth vertebra is like its predecessor, but smaller generally, while the united 
di- and parapophysial surface (on each side) is larger. 
With age, as the adult condition is gradually attained, the sacral vertebre become 
drawn relatively preaxiad through the much less rapid rate of increase of the last five 
lumbar vertebre (twenty-eighth to thirty-second). Thus these vertebrae become rather 
supraacetabular in position, as in Struthio, than postacetabular; and thus the vertebral 
column hardly appears, as it does in Struthio, at the bottom of the acetabulum when 
the pelvis is viewed laterally. 
THE SACRO-CAUDAL VERTEBR2. 
The thirty-siath vertebra.—In the young this vertebra has a tolerably developed 
centrum and a transverse process (formed of both di- and parapophysis) abutting 
1 Tt may be the 28th to the 32nd, or only the 29th to the 31st, that are thus devoid of transverse processes, 
VoL. X.—Part I. No. 2.—March, 1877. a 
