399 
The pleurapophysial plate is sculptured outwardly by longitudinal ridges and 
channels; the riblet loses relative length after the sixth or seventh cervical. The pre- 
and post-axial articular surfaces retain their essential character throughout, being con- 
cavo-convex in opposite directions; the fore surface is always superior in breadth, and 
this dimension, though less in the hind surface, is greater than the vertical diameter. 
A larger proportion of the neural surface of the fore end of the centrum is uncovered 
by the neural arch after the third and fourth cervicals. 
From the neck series are selected vertebra for views corresponding to some of those 
given by Mivart of the Ostrich, which best illustrate the modifications of such vertebree 
in the larger flightless bird. 
SIXTH VERTEBRA (i nat. size). 
Fig. 14. 
A eye az, 

i f 
ay i 
\) 
) { 
f ~ ™ 
Fig. 14, hemal (ventral) aspect. 
The hypapophyses in the sixth cervical (fig. 14, hy) are oblong, smoothly obtuse 
tuberosities. ‘The exterior of the parapophysial part (p) of the pleurapophysial plate 
(p, ps) is longitudinally channelled and ridged ; the riblet is shortened, as in Struthio!, 
but in a greater degree. The interzygapophysial bar, though short, leaves a foramen 
before it islost in the base of the postzygapophysis. ‘The metapophysis (fig. 14, m, m) 
is a mere slight outswelling of the diapophysial mass. The anterior depression at 
the hemal surface of the centrum is no longer defined; it is the beginning of the 
longitudinal channel h, banked by the hypapophyses. Behind these the surface is 
smooth and flat; then again becomes slightly concave transversely at the expanded 
hind part of the centrum, pe. 
* Mivart, Joc. cit. p. 400, fig. 25. 

