Thus we find the mechanism of the maxillary organs of the Wealden herbivorous saurian, as demonstrated by recent discoveries, in perfect harmony with the remarkable dental characters which rendered the first known teeth so enigmatical. In the Iguanodon we have a solution of the problem, how the integrity of the type of organization peculiar to the class of cold-blooded vertebrata was maintained, and yet adapted by simple modifications to fulfil the conditions required by the economy of a gigantic terrestrial reptile, destined to obtain support exclusively from vegetable substances; in like manner as the extinct colossal sloth-like Edentata of South America. In fine, we have in the Iguanodon the type of the terrestrial herbivora, which in that remote epoch of the earth's physical history--the _Age of Reptiles_--occupied the same relative station in the terrestrial fauna, and fulfilled the same general purposes in the economy of nature, as the Mylodons, Mastodons, and Mammoths, of the tertiary periods, and the large pachyderms of modern times. Although some important data are still required to complete our knowledge of the structure of the Iguanodon, we are warranted in concluding that this colossal herbivorous reptile was as bulky as the elephant, and as massive in its proportions: for, living exclusively on vegetable substances, the abdominal region must have been largely developed. Its limbs must have been of proportionate size to support and move so enormous a carcass. The hinder extremities probably presented the unwieldly contour of those of the Hippopotamus, and were based on strong short feet, protected by broad horny ungueal phalanges, or nails. The fore-legs appear to have been less bulky, and adapted for seizing and pulling down plants and branches: the teeth and jaws demonstrate the nature of its food; and the fossil remains of coniferous trees, arborescent, ferns, and cycadeous plants, with which its relics are commonly associated, indicate the character of the flora adapted for its sustenance.[139] [Footnote 139: Philosophical Transactions, for 1848, pp. 196-198.]