412 MR. ST. GEORGE MIVART ON THE 
The neural surface of the centrum is still more exposed than heretofore by the cutting 
away, as it were, of the preaxial part of the neural arch, which has a more marked 
median process. 
The ventral surface is nowhere concave transversely, though somewhat so antero- 
posteriorly; not, however, to the same degree as in the nineteenth vertebra. The 
preaxial margin is also somewhat less concave, and the postaxial margin less convex. 
There is a median hypapophysis which may or may not be somewhat expanded laterally 
towards its tip, and which may or may not project more strongly preaxiad than in the 
nineteenth vertebra, and may have its dorsal surface concave transversely. The ventral 
surface of its apex may be marked with a short, faint, antero-posterior groove, the last 
trace of the bifurcation of the process in more preaxial vertebre. 
The side of the centrum is continuous with that of the neural arch, exhibiting an 
undulating expanse (concavo-convex dorso-ventrally), which is smooth, save that there 
may be a scarcely perceptible indication of a ridge running obliquely ventrad from the 
capitular process to the postaxial margin of the centrum. 
The parapophysis extends less both preaxially and outwards than in the nineteenth 
vertebra; but the articular fossa for the head of the rib is larger, though nearly, if not 
quite, as deep (fig. 45, p). 
The diapophysis again projects more outwards, is more extended antero-posteriorly, 
and more remote from the parapophysis than in the preceding vertebra. It bears on 
its ventral side, more close to its external margin, a convex articular surface (fig. 45, d) 
for the tubercle of the rib, which surface is rather more elongated and less rounded 
than it is in the nineteenth vertebra. It is placed about as near to the preaxial margin 
of the diapophysis as to its postaxial margin, or rather nearer; and therefore more 
postaxially with relation to the whole, more extended, diapophysis than in the more 
preaxial vertebra. 
Ventral and preaxial to this surface the preaxial aspect of the neural lamina (pedicle) 
is deeply, widely, and irregularly excavated; and another excavation is placed near the 
postaxial margin of the pedicle, in the same position as in the nineteenth vertebra, but 
larger in size. 
The neural spine is more extended both dorsally and antero-posteriorly, having a 
straight dorsal margin, which about equals in length its preaxial margin and also the 
transverse diameter of the postaxial articular surface of the centrum. 
The postaxial excavation of the spine extends less dorsally, the dorsal part of the 
neural spine presenting postaxially a single margin, instead of a flat surface bounded by 
two ridges as in the nineteenth vertebra. 
From the side of the neural spine two lamine of bone proceed postaxially to the 
postzygapophyses, bounding externally that fossa behind the neural spine which repre- 
sents the postaxial excavation of that spine, which we have seen to exist in vertebrae 
nearer the skull. 
