CRETACEOUS REPTILES. 393 
of a broad, thin and flat bone (51), with a smooth emargination, and a rough or 
slightly granulated surface. As the broad, thin and anteriorly emarginate 
scapula of the Iguana presents a similar surface, I conclude the part in the fossil 
marked 51 to be the scapula ; and the short, thick, subcylindrical, hollow bone (53), 
slightly twisted and expanded at both ends, to be the shaft of the humerus: it is 
shorter in proportion to its breadth than in the existing Lizards, and probably 
supported a shorter fore-arm and fore-foot; the whole limb being therefore, 
perhaps, more formed for swimming than in the Monitors and Iguane. 
The ball-and-socket structure of the vertebrz is better adapted to sustain the 
body on dry land than the biconcave structure ; but the modern Crocodiles, the 
Amblyrhynchus, and the rare instance of the Lepidosteus amongst fishes, prove it 
not to be incompatible with aquatic habits. The Dolichosaurus, with a proccelian 
type of vertebrate structure, and amongst the earliest reptiles that manifested 
such structure, may well have been a good swimmer and frequenter of the 
ancient ocean of its epoch, as well as a crawler on dry land. Although the arti- 
culations of the vertebre must have limited if not prohibited the bending of the 
spine in the vertical direction, the extent of lateral flexuosity is considerable ; 
the double curve of the fore-part of the vertebral column, preserved in fig. |, 
being evidently the natural one assumed in the last struggles of the dying 
animal. 
Assuming that the specimens fig. 1. Pl. XX XVIII. and fig. 4. Pl. XXXIX. 
give the natural length of the neck and trunk of the Dolichosaurus, to which 
trunk the size of the anterior caudal vertebre indicate a long and strong tail to. 
have been appended, the progress of the long and slender Dolichosaurus through 
the water would be by flexuous and undulatory lateral movements of the entire 
body, like those of a water-snake or eel. 
The specimen fig. 1. Pl. XXX VIII. demonstrates that this proccelian Lizard of 
the cretaceous period had a smaller head and a longer, more slender and tapering 
neck than any known existing species of the Lacertian order of Reptiles. 
The hinder moiety of the trunk-vertebre, with part of the pelvis and root of 
the tail,—which, from the correspondence of size, shape and structure of the 
vertebre, I refer to the Dolichosaurus, and from the evidence above given, corro- 
borated by the disposition of the parts in the chalk-matrix, I believe to be part of 
the same skeleton as the anterior moiety, fig. 1. Pl. XXX VII.—includes twenty- 
one abdominal, two sacral, and five caudal vertebree. They have been exposed by 
the removal of the chalk from their inferior or ventral surfaces, the operation 
