PHYLOGENY OF THE PALHZOGNATHZ AND NEOGNATH 2. 213 
The Ist caudal bears both para- and diapophyses. Sometimes the former fuse with 
those of the sacral. Behind this lie seven caudals without parapophyses, before the first 
free caudal is encountered. ‘The neural spines of these are not transversely expanded 
as in Casuarius. 
In Rhea there are ten pre- and five post-sacral vertebre. 
The pre-sacral comprise two thoracic, four lumbar, and four lumbo-sacral; the last 
of these may develop parapophysial processes. 
The sacral ribs fuse with the ilium more dorsad than in Struthio, Caswarius, ox 
Dromeus. In the last three they abut more or less extensively against the post-acetabular 
ascending process of the ischium. In Rhea they rise dorsad, so as to reach the level 
of the centre of the acetabular arc. 
The Ist sacral is intermediate in position, with regard to the acetabulum, between 
Casuarius and Struthio. In the latter, it will be remembered, it lies considerably behind 
the acetabulum, in Caswarius level with its hinder border. 
The sacral ribs are very short and almost indistinguishably fused with their 
diapophyses. In the possession of diapophyses these vertebre differ from those of. 
Casuarius and Dromeus, and resemble Struthio, in which, however, they are much 
more extensively developed. 
The first post-sacral, or 1st caudal, bears both para- and diapophysial processes, 
but they are almost indistinguishably fused. The 2nd caudal bears diapophyses only. 
The 8rd to 5th caudals are somewhat remarkable in that they are represented only by 
atrophied vertebre. The centra of these are reduced to thin delicate rods, supporting 
slender diapophyses and feeble neural spines. ‘The 6th vertebra resembles the 5th, 
but has a stronger neural spine. It is the first vertebra to escape from the clasp of 
the post-acetabular ilium. The 7th has a much stronger neural spine and slightly 
thicker centrum, but like the 6th has lost its diapophyses. The 8th and 9th have 
inflated cancellous centra and short neural spines; they fuse by their ventral aspects 
with the ischia. The 10th is the first free caudal, of which there are eight in all: 
these have short thick centra and short neural spines. 
In Apterya there are nine pre- and five or six post-sacrals, with the true sacrals 
sixteen in all. 
The pre-sacrals represent two thoracic, four lumbar, and three lumbo-sacral. The 
first post-sacral (1st caudal) bears short para- and diapophysial processes. The post-sacral 
are chiefly remarkable for the great lateral compression which they have undergone. 
The synsacrum of the Dinornithide differs in many respects from that of all the 
It resembles in many ways that of Dromeus and Casuarius 
other Paleognathe. 
The pre-sacrals are apparently 
on the one hand, and that of Séruthio on the other. 
eleven in number, viz., two thoracic, six lumbar, and three lumbo-sacral. ‘There is an 
indication of a fourth lumbo-sacral bearing parapophysial processes, which have almost 
completely fused with those of the Ist sacral. There are five post-sacrals. 
VoL. xv.—PArt v. No. 14.—December, 1900. 2u 
