262 
FOSSIL CROCODILES 
guished by their conical form, striated surface, and 
lateral edges, but more particularly by their internal 
structure. Fig. 3. represents a fossil tooth from 
Til gate Forest. They never become solid, but 
consist, as it were, of a series of cones enclosed 
within each other, the outer cone, or old tooth, being 
burst by the pressure of the included one, as the 
latter increases in size. Hence, at whatever age a 
tooth is removed, we find either in the socket or the 
cavity of the tooth, a small tooth ready to occupy the 
place of the old one, wlien the latter is destroyed 
by age or accident. This succession is repeated 
very frequently ; and it is from this cause, that the 
fossil teeth of these animals are always so sharp 
and well defined ; for although larger when old, 
they are not less perfect than in the young state. 
The lateral ridges are placed anteriorly and pos- 
teriorly. 
Teeth of the Crocodiles of Tilgate Forest. 
(Figs. 2, 3. p. 261.) — These will be found to present 
all the essential characters of the teeth of the recent 
teeth and bones occur in the Stonesfield slate, Purbeck lime- 
stone, &c. and in the Hastings formation ; we have not observed 
them in the Shapklin sand, nor in the Galt ; but they are found, 
though very rarely, in the lower chalk. M. Cuvier mentions, as a 
solitary instance, a crocodile’s tooth in chalk from Meudon. It should 
be remarked, that there are occasionally found in the chalk, teeth of a 
conical form, and longitudinally striated, which, from their external 
appearance only, might he taken for those of crocodiles ; hut an ex- 
amination of their internal structure readily distinguishes them. Mr. 
Parkinson describes the remains of a crocotlile found in the London 
clay at Hackney, in which the vertebrae were concavo-convex, as in 
the recent species.* The head of an alligator was found in tlie Lomlon 
clay, of the Isle of Sheppey, during tlie last year (1832). 
* Varkiiison's liilml. Org. Rem. p. 387. 
