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, or of very 

 rare occurrence. At the period of the formation of these deposites, 

 turtles, 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 Iguanodon, (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 vertebrae, claw-bones, and other pans of the skeleton, bear 

 the same relative proportions. This creature, like some of the recent 

 species of Iguanas, had tvaris or horns on its snout, and an appendage 

 of this kind has been found of the size and shape of the lesser horn 

 of the rhinoceros ! From the prevailing character of the form of the 

 bones, it is probable that this animal was shorter in proportion to 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 individu- 

 als attained a height of nine or ten feet, and were from sixty to a 

 hundred feet in length! A circumstance even more extraordinary 

 than its, magnitude, is that of its having performed mastication like the 



