OF TILGATE FOREST. 
281 
bably belonged to a saurian animal. It is well known 
that some reptiles of that order have bony or horny 
projections on their foreheads ; and it is not a little 
curious, that, among the Iguanas, the horned species 
most prevail. The Iguana cornuta^ which is a native 
of Saint Domingo, resembles the common Iguana in 
size, colour, and general j)roportions ; on the front 
of the head, between the eyes and nostrils, are 
seated four rather large, scaly, tubercles ; behind 
which rises an osaeous conical horn, or process, 
covered by a single scale.* That our fossil was such 
an a])pendage, there can be no doubt ; and its sur- 
face bears marks of the impression of an integument 
by whicli it was covered, and probably attaclied to 
the skull. This fact establishes another remarkable 
analogy between the Iguanodon, and the animal 
from which its name is deri\ ed. 
Plesiosaurus. The vertebnr, teeth, and other 
bones of this extraordinary genus, whose osteology 
has been so admirably and so fully described by Mr. 
Conybearet, occur in the strata of Tilgate Forest, 
* Shaw’s Zoology, vol. iii. part i. p. 203. 
f Geological Transactions, vol. v. and vol. i. new series. It may- 
be interesting to the general reader to state, that the Plesiosaurus and 
Ichthyosaurus are two genera of fossil animals, supposed to have 
been oviparous, and to belong to the family of the sanrians, but differing 
very essentially from all existing species, and in inch particulars as 
evidently must have fitted them to live entirely in the sea. Their 
vertebra: are deeply cupped like those of fishes, and are as thin as 
those of the shark, so as to admit of a vibratory motion of the tail, to 
assist progression. The extremities terminate in four paddles, com- 
posed of a series of flat polygonal bones, greatly exceeding in number 
even the phalengic cartilages of the fins of fishes. The most won- 
derful animal of this division is the Plesiosaurus doUchodeirus, or long- 
necked [)lesiosaurus : the neck of this animal is equal to half the 
entire length of the body and tail uniteil, ami is composed of 3b ver- 
