206 DESCRIPTION OF REPTILES. 
Description of the remains of the Fossil Reptiles from the Tertiary deposits 
of Bracklesham and Bognor, in the Museum of Freprericx Dixon, 
Esq., or figured in the present Work. By Proressor Owen, F.R.S. 
Class REPTILIA. 
Order CROCODILIA, Owen. 
Tue existing species of the order Crocodilia* all belong to the section with 
procelian vertebre, or those having the fore-part of the vertebral body concave, 
the hind-part convex ; and they constitute the types of three genera; which, 
besides being marked by certain characters of the tegumentary and perishable 
parts, are distinguished by others imprinted upon the enduring and fossilizable 
framework, viz. the bones and the teeth. Of these characters the most decisive 
and constant are afforded by the size, form and proportions of the teeth, and 
the relations of certain teeth of the under jaw to pits or grooves in the upper 
jaw. For example, ‘‘the reception of the fourth or canine tooth of each ramus 
of the lower jaw into a pit in the palate, where it is concealed by the upper jaw 
when the mouth is shut,” is a character of the genus Alligator ; ‘‘ the reception 
of the corresponding teeth in notches, one on each side of the border of the 
upper jaw, where they are exposed to view when the mouth is shut,” is a 
character of the genus Crocodilus. In both Alligator and Crocodilus the skull is 
depressed, the jaws thick and not very long, the borders of the jaws festooned, 
and the teeth of unequal size: the muzzle is broad and obtuse in most of the 
* ©Report on British Fossil Reptiles’ in ‘ Report of British Association’ for 1841, p. 65. In this 
Report I separated the Crocodilia, as an order, from the Lacertilia, Dinosauria, Pterosauria, and 
Enaliosauria, belonging to the great and diversified order Sawria of Brongniart and Cuvier. The 
existing forms of my order Crocodilia belong exclusively to the first section, or those “ with concavo- 
convex, or procelian vertebra,” which section answers to the group defined and called ‘ Loricata’ by 
Merrem (Tentamen Systematis Amphibiorum, 8vo, 1820), and H’mydosauria by MM. De Blain- 
ville and Gray. The order ‘ Crocodilia,’ as defined in my ‘ Report,’ includes, however, some extinet 
species not admitted into the ‘ Zoricata’ of Merrem, and excludes others which are ranked amongst 
the Loricata of Fitzinger, and the Emydosauria in the British Museum ; I, therefore, found myself 
compelled to propose a distinct name (Crocodilia) for such differently constructed order. 
