198 
DR. MANTELL ON THE IGUANODON. 
inent of the lower lip and the integuments of the jaws, as indicated by the size and 
number of the vascular foramina, present a striking analogy to the Edentata, with 
which indeed other parts of the osteology of the Iguanodon bear a remarkable resem- 
blance ; as for example, the sacrum formed by the anchylosis of five vertebrae, the 
expanded vertebral portion of the ribs, &c. ; while the massive femur with its me- 
dullary cavity, well-marked trochanters and condyles, and the short and strong 
metatarsal and phalangeal bones, remind us of the gigantic recent pachyderms. 
In fine, we have in the Iguanodon the type of the terrestrial herbivora, which 
in that remote epoch of the earth’s physical history, termed by geologists “ The Age 
of Reptiles" occupied the same relative station in the scale of being, and fulfilled the 
same general purposes in the economy of nature, as the Mastodons, Mammoths, and 
Mylodons of the tertiary periods, and the large pachyderms of modern times. 
Although many important characters af the osteology of the Iguanodon are still 
unknown, we may, 1 conceive, from the data hitherto obtained, safely infer that this 
gigantic herbivorous reptile was equal in bulk to the Elephant, and as massive in its 
proportions ; for living exclusively on vegetables there must have been a large deve- 
lopment of the abdominal region. Its limbs must have been of proportionate size to 
sustain and move so enormous a carcass. The hinder extremities in all probability 
presented the unwieldy contour of those of the Hippopotamus and Rhinoceros, and 
were supported by strong short feet, protected by broad horny ungual phalanges. 
The fore-legs appear to have been less bulky, and adapted for seizing and pulling 
down plants and branches of trees. The teeth and jaws demonstrate its power of 
mastication and the nature of its food ; and the remains of coniferous trees, arbo- 
rescent ferns and cycadeous plants, with which its relics are commonly associated, 
indicate the character of the flora adapted for its sustenance. 
I forbear entering at this time upon other considerations relating to the fossil 
reptiles of the Wealden, in the hope of being able to lay before the Royal Society, on 
some future occasion, an account of several other interesting Saurian remains from 
the strata of Tilgate Forest ; but I beg to subjoin the following supplementary 
remarks on my last memoir. 
Regnosaurus Northamptoni, Phil. Trans. 1841, Plate V. figs. 1, 8. — The portion of 
the lower jaw of a Saurian formerly described as that of a young Iguanodon*, is 
proved by the specimen discovered by Captain Brickenden, to be generically or sub- 
generically distinct from the I. Mantelli, although unquestionably belonging to the 
same remarkable family of herbivorous reptiles ; and the internal structure of the 
teeth in this specimen, so far as I can judge from a microscopical examination of a 
very small fragment from the upper part of the fang, corresponds more nearly with 
that of the Iguanodon than with the very fine and dense tooth-ivory of the teeth of 
* Philosophical Transactions, 1841, p. 131. 
