395 
The ridges on the fore part of the hemal surface of the centrum in Struthio! are 
not present in Dinornis maximus or in D. robustus. The parapophysis is represented 
by the short obtuse ridge, p, figs. 4 & 7; the pleurapophysis (ib. pl) by a similar one 
above, near the middle of the outer wall of the vertebrarterial canal, v. From the 
diapophysial plate (fig. 6, d), completing that wall above, a ridge (fig. 4, 7) extends back- 
ward to the postzygapophysis, z’; this ridge circumscribes externally the vertical canal 
(figs. 4 & 7, s). On the medial side of this canal is the pneumatic orifice (fig. 7, 4), 
leading to the cancellous part of the neurapophysis, The canal s is not noted in 
Strathio, and in place of one large hole there are irregular pneumatic foramina”, ‘The 
postzygapophysis is thrice the size of the prezygapophysis, but the antero-posterior hardly 
it at all exceeds the transverse diameter; its aspect is as in Struthio and birds gene- 
rally, The hyperapophysis (figs. 4 & 6, hp) is relatively more promment than in 
Struthio. The neural spine gains thickness as its base extends backward; its summit 
is broken off in my specimen, exposing the wide-celled pneumatic texture. 
In Dinornis elephantopus the hyperapophyses (fig. 5, kp) are relatively larger and 
higher; the prezyapophyses are relatively less. 
The odontoid process (figs. 4 & 7, ca) is less than half the size of the atlantal hyp- 
apophysis; its free extremity is obtusely rounded, 
The third cervical vertebra, as in Struthio and birds generally, gains a transverse 
breadth of the neural arch, anteriorly, with concomitant size of the prezygapophyses 
(fig. 11, 2), fitting the postzygapophyses of the axis. From this gain results a quadrate 
form of the roof of the vertebra; but, from the less relative length or greater breadth 
of this part in Dinornis, the roof (fig, 11) is a transverse quadrilateral, not so oblong as 
in Struthio: in both birds the angles are rounded off*, 
The centrum is a horizontal wedge, with the edge anterior, concave, and formed by 
the neural border of the preaxial articular surface (fig. 9, @¢), which, broad and con- 
cave transversely, is short and almost flat vertically, but here slopes from the vertical 
so much backward that it is on a plane with the contour of the hamal surface of the 
centrum, as carried back by the hypapophysis (Ay), and forms a yery open angle, with 
the base-line extended from its hemal border to the same border of the postaxial 
surface, Hence, in a direct front view (fig. 9), alittle more than the concave fore border 
of the preaxial surface (a¢) is seen: while the whole surface is fully in view in the 
under view ofthe vertebra (fig. 10, ac). It looks almost wholly downward (heemad) in 
Dinornis, not obliquely downward and forward (heemo-preaxiad) as in Struthio 4, 
The postaxial surface (fig. 8, pe) much resembles that of the axis vertebra: its trans- 
verse contour is sinuous, a medial convexity dividing two concavities; the aspect is 
rd; the verti : ransverse «i oY in a 
more upward than backward; the vertical exceeds the transverse diameter, but 
minor degree than do the reverse proportions of the preaxial surface. 
* Th. loc. cit. p. B93. 
4 Th, oe. cit, p. S04. 
3Q2 
| Mivart, Toc. cvt. p. 891, fig. 12, ¢. 
8 Th. loc. cit. p. 395, fig, 15. 
