PHYLOGENY OF THE PALASOGNATHA AND NEOGNATH. 209 
line to form two high curved ridges sloping downwards and backwards to terminate in 
metapophyses. At about the 15th vertebra the two ridges again coalesce and form a 
very high vertical transverse neural spine. From the 18th backwards this gradually 
becomes more and more laterally compressed, so as to pass insensibly into the typical 
neural spines of the thoracic vertebre. Every neural spine, from that of the axis 
backwards, bears a fossa at its base, both anteriorly and posteriorly. The latter is the 
deeper. The vertebre from the middle of the neck backwards have these fossee of 
very considerable size. They lodge a ligament. 
From 6-10 in C. casuarius and C. c. australis the diapophysis sends back a bar of 
bone to the hyperapophysis. 
The vertebre are all pneumatic. In the hinder cervicals there is a large pneumatic 
aperture dorsad of the interzygapophysial ridge. In the thoracic there are several 
yery large ones—one below the transverse process, one between the transverse process 
and the postzygapophysis, and one dorsad, lying between the anterior zygapophysis 
and the base of the neural spine. This last is represented by a deep fossa in Dromeus. 
The aperture ventrad of the anterior zygapophysis is feebly developed or wanting in 
Dromeus. 
The cervical ribs (pleurosteites) and hypapophyses resemble those of Dromeus. 
In Dromeus the vertebre are less specialized than in Casuarius. The high 
transversely expanded neural spines are wanting, though the ligamental neural fosse, 
especially that caudad of the neural spine, are very deep. ‘The pneumatic fossa in, or 
above, the interzygapophysial ridge is very deep, as also is that lying at the base and 
in front of the neural spine. The sides of the fosse, moreover, are smooth, not obscured 
by cancellated tissue as in Caswarius. 
In Struthio the centra of the vertebra are relatively much longer than in Dromeus or 
Casuarius. The neural spines of the anterior cervicals are long, low, and rise to form 
a sharp median ridge. The ligamental fosse are narrow grooves channelled out of 
this ridge. The posterior cervicals have the neural spines wider and shorter, antero- 
posteriorly, and they are deeply hollowed for the ligament. 
The cervical ribs, as in Casuarius and Dromeus, are long, but more slender than in 
these. As in Dromeus they fuse with a plate of bone depending from the diapophysis 
and a lateral parapophysial outgrowth from the anterior end of the centrum below 
the prezygapophysis. The presence of this rib serves to enclose a canal for the 
vertebral artery. One great point of difference between this region of the vertebra and 
that in Dromeus and Casuarius lies in the fact that in Struthio the lamella depending 
from the diapophysis, and with which the rib articulates, is continued backwards along 
the centrum for a considerable distance, forming an extensive and tunnel-like passage 
for the artery. 
The pneumatic apertures are not so conspicuous as in Dromeus. 
he interzygapophysial ridge of the anterior cervicals as in Dromeus. In 
There is no 
aperture in t 
