394 CRETACEOUS REPTILES. 
having been commenced from the opposite side of the block from that at which 
the exposure of the part of the skeleton in the other portion of the same block 
of chalk has been effected. The bodies of the vertebrz and the ribs show the 
same disposition and slight degree of dislocation as in the specimen. The ribs 
have been pressed by the weight of the surrounding chalk, as the soft parts 
yielded and became decomposed, close to the sides of the vertebrae, but with 
scarcely any further dislocation ; and the vertebree, maintaining the close arti- 
culations of their cup-and-ball surfaces, continue, with not more deviation from 
the straight line than a slight flexuosity, like that shown by the last six vertebra 
in the moiety of the skeleton in Pl. XX XVIII. 
The under surfaces of the vertebre exhibit the same smooth, imperforate, 
longitudinally concave, transversely convex surfaces, as in the anterior dorsals 
of the last-described specimen: as in that specimen, also, they are longer in 
proportion to their breadth than in the Monitor (Varanus ?) figured by Cuvier*, 
or than in the Iguana, Cyclodus and Tiliqua: the diapophyses rise by a shorter 
base than in the Zguana: in an Australian Tiliqua I find the under surface of the 
centrum with two vascular perforations towards its fore-part, which are not pre- 
sent in the Dolichosaurus, nor in many of the existing Lacertians. Each diapo- 
physis forms a short rounded tubercle, immediately below the base of the ante- 
rior zygapophysis ; and the simple, slightly expanded head of the rib is excavated 
to fit the tubercle. In the degree of compression and expansion of the proximal 
portions of the ribs, and in their curvature, the present precisely corresponds 
with the preceding portion of the skeleton of the Dolichosaurus ; and it is obvious 
that the natural form of the abdomen must have been deep and narrow, like that 
of the Water-Snakes (Hydrophides). 
The length of the last two abdominal vertebre slightly decreases: a short, 
slender, nearly straight and pointed pleurapophysis projects outwards from the 
diapophysis of the last abdominal (lumbar) vertebra with which it has become 
anchylosed. The pleurapophyses of the next two vertebra are equally confluent 
with the diapophyses, but are rather longer and much thicker than those of the 
preceding vertebra: they are also slightly expanded and truncate at their ends ; 
they determine by these proportions the ‘ sacral vertebre,’ which thus agree in 
number, as in general structure, in the Dolichosaurus with those in existing 
Lacertians. 
Part of the bodies of the two sacral vertebre has been destroyed, but evident 
* Ossem. Foss. v. pt. ii. pl. 17. fig. 23. 
