AXTAL SKELETON OF THE OSTRICH. 389 
Its pre- and postaxial margins would be nearly parallel, but that the latter is en- 
croached on by the lateral extensions preaxiad of the postaxial articular surface, as 
before mentioned. 
Its preaxial margin is similarly, though to a less extent, encroached on, on each side, 
by the postaxiad lateral extensions of the preaxial articular surface. The little lateral 
facets thus formed on each side of each end of the dorsal (or neural) surface articulate 
with the sides of the odontoid process of the axis (fig. 5, p ¢). 
The ventral surface of the quasi-body is gently convex from side to side, and slightly 
concave antero-posteriorly in its middle. 
Its preaxial margin is generally slightly concave, though it may be (as in specimen 
1362 B) slightly convex; its postaxial margin is nearly straight, except for the sudden 
production postaxiad of the median hypapophysial process before referred to (fig. 6, hy). 
This process has a width equal to about a third of that of the postaxial surface of the 
quasi-centrum ; and the length of its free projection may nearly equal or may slightly 
exceed its breadth. 
A small rounded tubercle or lateral hypapophysial process (figs. 4, 6, 7) may be 
developed on each side of the root of the median hypapophysial process, close to the 
postaxial margin of the ventral surface of the quasi-body ; and a slight ridge may run 
obliquely outwards and preaxially from each of these tubercles nearly to the preaxial 
margin of such ventral surface. 
The hypapophysial process is directed postaxiad, and but slightly ventrad ; indeed its 
free extremity (as in specimen 13628) may have a slightly dorsal curvature. 
The dorsal surface of this process articulates with the middle of the front part of the 
ventral surface of the centrum of the axis vertebra. 
The neural arch may be considered as consisting of two lateral halves dorsally united 
in the middle line. 
Each lateral half springs from the side of the quasi-centrum by a narrow portion or 
pedicle, expanding dorsally into a neural lamina. 
A narrow band or a mere spiculum of bone (figs. 2 & 3) may spring from the more 
postaxial part of the side of the quasi-centrum, and may fuse above with the posterior 
part of the pedicle, forming a foramen or short bony canal for the vertebral artery. The 
preaxial margin of the pedicle is strongly concave, but develops no process of any kind. 
Its postaxial margin is also strongly concave, and ends above in a decided postzyga- 
pophysis ; but before reaching that postzygapophysis it develops a more or less marked 
rounded prominence, which is a rudimentary tubercular process or diapophysis’ (figs. 2, 
3, & 5, d). 
The little band or spiculum of bone before noticed, wherever it is developed, fuses 
' T use the word diapophysis to denote all parts which are homotypes of the process articulating with the 
tubercle of the rib when this exists. Similarly I employ the term parapophysis to denote the part with which 
the head of the rib articulates. 
