214 MR. W. P. PYCRAFT ON THE MORPHOLOGY AND 
The pre-sacrals resemble those of Dromeus and Caswarius in that they descend 
below the level of the ventral border of the pre-ilium, but not greatly so. In Struthio 
this feature is much more marked, the whole centrum and base of the neural spine 
being exposed in side view. The parapophysial processes of the first caudal are 
directed backwards instead of forwards. From this cause the true sacral vertebre 
are completely isolated. 
In Struthio, Casuarius, Dromeus, and Apteryx, it will be remembered, the para 
pophysial process of the first or even first and second caudals may combine with 
those of the true sacrals to form a sacral mass, the true nature of which is difficult 
to make out in the adult. The post-sacrals (caudals) resemble those of Struthio 
rather than any other Ratitw in the great development of the diapophysial process, 
which extends upwards, outwards, and backwards to separate the post-acetabular 
ilium. 
In Dinornis, however, this separation of the post-acetabular ilia is carried to a 
greater length than in any other Ratite. ‘The neural spines of the Dinornithide are 
peculiar in that they combine dorsally to form a broad lozenge-shaped superficial plate 
of bone which serves as a cover to the huge fossa that otherwise exists between the 
upwardly directed transverse processes and the post-ilia. 
The synsacrum of the Crypturi differs from that of all the other forms herein 
described. Moreover, in the points wherein it differs from these it resembles the 
Neognathe. 
One of the most noticeable differences is the fact that the post-sacrals have lost their 
neura) spines. In all the flightless Palwognathe these are of great length. ‘The 
diapophyses of the post-sacral region rise from the top of the centrum, at the base of 
a long, faint, median ridge marking the position of the neural spines in other forms. 
These diapophyses develop thin plates of bone which fuse one with another to form a 
lozenge-shaped plate, protecting the inter-diapophysial fossz, as is done by the similar 
plate from the neural spines in Dinornis. 
‘The synsacrum of the Tinamous includes one thoracic, four lumbar, five lambo-sacral, 
and five post-sacral. There are no parapophysial processes abutting against the 
pectineal process as in the flightless Palwognathe. This process, it should be 
mentioned, has shifted further backward relatively to the sacral vertebre, so that a 
line drawn across from the base of the anterior concave border of the one would pass 
immediately in front of the first sacral. 
The sacral ribs are very long, and articulate with the illum immediately behind the 
acetabulum by a long vertical roughened surface. The rib of the second sacral is 
vestigial or wanting. 
The free caudal vertebree in the Palwognathe do not exceed ten in number. Some- 
times the 9th and 10th are more or less fused. 
In Séruthio the 10th is laterally compressed to form a kind of pygostyle. 
