Fig. 
. Side view of a hinder dorsal vertebra. 
. Back view of ditto. 
. Two caudal vertebree. 
Lacertians. 
PLATE 1. 
Mosasaurus gracilis, nat. size. 
From the Upper Chalk, near Lewes. In the Mantellian Collection, British 
Museum. 
Mosasaurus Hoffmann. 
. Side view of a hinder dorsal vertebra, nat. size. 
. Back view of ditto. 
From the Cretaceous Beds, at Maestricht. In the British Museum. 
. The half of a vertically and longitudinally bisected vertebral centrum of a 
Mosasaurus gracilis, which was partially enclosed in a nodule of flint, from 
the Upper Chalk, at Kemptown, Brighton. The siliceous matter has 
infiltrated itself into much of the cellular structure of the middle part of the 
centrum. The densest part of the cellular structure is near the concave 
surface of the vertebra. 
In the Collection of Dr. Mantell, F.R.S., by whose obliging permission it is 
figured for the present Monograph. 
