46 
PEOFESSOE OWEX OX SOME EE^VIAIXS OF 
The length of the centrum is 3 inches ; the vertical diameter of the vertebra is 2 inches 
10 lines. The greatest vertical diameter of the neural canal is 6 lines. 
The third vertebra of the present gigantic Lizard consists of a mutilated centrum only 
(Plate VIII. figs. 3 & 4) : it sho-ws the median tract defined by the lateral grooves 
(fig. 3, v) on the under surface, the grooves being broader and deeper and more decidedly 
bent out-ward at their fore-part than in the foregoing and some-what smaller vertebra ; the 
median tract is simply convex from side to side, and is straight length-wise ; it does not 
project at any part belo-w the level of the under surface ; on the contrary, the convex 
outer sides of the grooves project belo-w its level. The part of the neural canal (fig. 4), 
preserved on the upper broken surface, sho-ws the transverse expansion at its fore-part, 
and a lo-w median ridge from the floor of that part of the canal. 
The mid-tract of the lo-wer surface of the centrum {ib. fig. 3), though, in the cenical 
and anterior dorsal vertebree, defined by the lateral grooves, v, is not produced at any 
part as a hypapophysis, but resembles, in this respect, the under surface of the hinder 
neck-vertebrge in the Monitors ( Varanus, Hydrosaums, fig. 3 a). 
The small vertical diameter of the centrum, in proportion to its breadth, and the 
oblique position of the terminal cup and ball, are -well displayed in the present mutilated 
specimen, which appears to have been rolled and water-worn. 
In comparing the vertebrae of Megalania with those of existing Lizards, the biconcave 
vertebrae of the Geckos, and the complex procoehan vertebrae, with zygosphene and 
zygantrum, of the Iguanians*, are at once set aside; as are also the compressed and 
carinate or subcarinate cer-ncal and dorsal vertebrae of the Mhynchocejyhalus [Hatteria, 
Geay) of New Zealand. Among the less modified vertebrae of other Lacertians, those 
of the Australian Monitors and Lace-lizards [Hydrosauriis, Waglee) make the nearest 
approach to the vertebrae of Megalania. 
They present the same oblique position of the cup and ball (Plate VIII. figs. I a, 2 a), 
flatness and breadth of the under surface of the centrum [ib. fig. 3 «), constriction at the 
base of the ball and lateral expansion thence forwards to the costal tubercle ; the same 
relative size and aspect of zygapophyses; the same curVlinear pittings and fine -wrinklings 
afiecting the otherwise smooth and compact outer surface of the bone; the same con- 
trast between the vertical and transverse diameters of the two outlets of the neuml 
canal ; and the same lateral and infero-median ridges in that canal. The chief distinc- 
tions are, the much more contracted area of the neural canal, and the minor develop- 
ment of the neural spine, in Megalania (compare fig. 4 -with 4 a) ; also the shortness of 
the vertebrae in proportion to their breadth, in the large fossil Lizard. 
In Hydrosaufus varius the ridge representmg the neural spine begins, as in Megalania., 
at the fore-part of the neural arch, but is relatively higher, although low and equal : 
this makes it probable that the homologous ridge in the vertebra (Plate VIII. fig. 4, n s) 
* 0-wEX, ‘ Catalogue of the Osteological Series in the Museum of the Eoyal College of Surgeons,’ 4to, 
vol. i. 1853, p. 145, no. 668 ; and ‘ Prineipes d’Osteologie Comparee,’ 8vo, Paris, 1855, pi. 13 a, fig. 11 
