FOSSIL VARANIDAE AND MEGALANIDAE. 
397 
canal is very narrow and is here also, as with other vertebrae (cervical 
and caudal vertebrae), provided on its ventral region with three horizontal 
crests : a median one (crista medialis canalis vertebralis mihi) beginning 
under the shape of a small triangle not far from the ball and passing 
from here beyond the posterior half of the vertebra, disappearing gradually 
in the anterior one, or rather widening to such an extent, as to form a 
broad, basal, arched elevation in the spinal canal ; on both sides of this 
latter we see two deep lateral »rows, first converging then diverging 
'towards the front part of the vertebra (sulci laterales canalis vertebralis 
mihi) ; in V. marathonensis these furrows are only quite slightly 
marked, not deepening anywhere, so that in this species, 
the spinal canal is narrower in consequence of the massive structure of 
its ventral region ; above these we find in V. griseus two sharp lateral 
crests, which in V. marathonensis are stouter and less protruding, thus 
also less striking (crist æ laterales canalis vertebralis mihi) ; these are 
practically no more on the centre but extend along the whole length of 
the spinal canal on the basal part of the upper arch. 
Measurements : 
Length of centre * (median) 1 : 20*87 
Width of cup: 12*45 
Height of cup: 7*91 
Width of ball**: 11*1 
Length of ball (in median line) : 7 
Thickness of ball (measured in the median vertical line) : 5*71 
The greatest breadth of centre*: 20*62 
Median breadth of upper arch (on right side measured from intact 
point): 18*28 
Breadth of upper arch measured at the beginning of the strangulation 
before proc. obi. post.: 11*1 
Length of proc. obi. ant. measured in an oblique line from the basal 
excavation: 8 
Distance between the right proc. obi. post, and the median line of 
♦the fractured surface of proc. spinosus : 9*4 
Distance between posterior base of proc. spinosus and upper margin 
of posterior outlet of spinal canal: 7*9 
Median height of spinal canal in front : 8*2 
1 Slightly damaged parts are marked with one, very imperfectly preserved ones 
with two asterisks. 
