362 Geological Age of Reptiles. 
cient epoch has not been satisfactorily explained, and it would be 
foreign to our present purpose to enter into any discussion upon the 
subject; the intermixture of terrestrial remains with those of marine 
origin, may of course have been effected by the agency of a river 
or current. In the Stonesfield slate we first meet with the remains 
of that gigantic reptile, the Megalosaurus, (Great Lizard.) This 
monster, which, from the form of its teeth and skeleton, is evidently 
allied to the Monitor, must have been nearly forty feet in length, and 
seven or eight in height, and was probably a terrestrial animal. The 
crocodiles of this ancient epoch appear to have been exceedingly nu- 
merous, and belonged to species distinct from those of the present 
period, a great proportion being referrible to the Gavials; that divis- 
ion which has long slender snouts. 
In the fresh-water formations that intervene between the oolite and 
the chalk, namely, the Purbeck, Hastings’ sands and clays, and the 
Tilgate grit, the remains of several of the genera of the reptiles we 
have before noticed, occur; but those which are strictly marine, 
such as the Ichthyosaurus, are either altogether wanting, oF of very 
rare occurrence. At the period of the formation of these deposites, 
both marine and fresh-water, existed in great numbers, hav- * 
ing for contemporaries the Megalosaurus, one or more species of 
Plesiosaurus, several species of Gavials and Crocodiles, and proba- 
bly Pterodactyles. At this epoch we have also an enormous herbiv- 
orous reptile, essentially differing from any of the oviparous quadru- 
peds now existing, and surpassing in magnitude even the Megalo- 
saurus. This is the Jgwanodon, (so named from its teeth resembling 
those of the recent Iguana.) A thigh-bone of this creature, twenty 
three inches in circumference, has been discovered in the grit of Til- 
gate forest; the teeth are as large as the incisors of the rhinoceros, 
and the vertebra, claw-bones, and other parts of the skeleton, beat 
the same relative proportions. This creature, like some of the recent 
species of Iguanas, had warts or horns on its snout, and an appendage 
of this kind has been found of the size and shape of the lesser hora 
of the rhinoceros! From the prevailing character of the form of ” 
bones, it is probable that this animal was shorter in proportion 0 its 
bulk than the recent lizards, to which it is more nearly allied ; and 
marvellous as it may appear, we cannot but infer that some ! dividu- 
als attained a height of nine or ten feet, ‘and were from sixty ' a 
hundred feet in length! A circumstance even more extraordinay 
than its magnitude, is that of its having performed mastication like the 
