﻿12 FOSSIL REPTILIA OF THE 



with that shown by the present specimen (compare ' Monograph on the Fossil Reptilia of 

 the Wealden/ Supplement No. 3, Pal. vol. for 18G2, PI. X, fig. 4, with fig. 9, PI. 

 II, of the present Monograph). 



In like manner the inner surface of the smaller mandibular fragment (ib., fig. 10) shows 

 a gentle convexity lengthwise and an almost level surface vertically, broken by a longi- 

 tudinal groove near the lower border. 



Concluding that, as in Iguanodon, the germs of successional teeth would lie on this 

 side of the roots of the broken ones which had been in use, and that such germs would 

 have the ' lanceolate and acuminate ' portion of the crown, yielding the required test of con- 

 formity or otherwise in regard to marginal serration, I removed the inner (splenial) plate 

 at parts which exposed three such germs (PI. II, fig. 11, a , I, d), each demonstrating the 

 character in question. 



The inner side of the crown is traversed longitudinally by the submedial primary 

 ridge, the coronal margin anterior to which shows four acute serrations, with grooves 

 continued from their intervals some way down the surface. The extreme fragility of these 

 precious evidences checked further attempts to expose more of that surface. My inter- 

 pretation of the characters of the mandible and mandibular teeth, so far as they are 

 exhibited by this specimen, is, that they demonstrate a reptile of the genus Iguanodon. 



If the specimen belong to a full-grown individual, the greater relative size and the 

 smaller number of the coronal serrations show it to belong to a distinct species of Iguanodon, 

 for which the name of its discoverer is deservedly to be retained. 



Still may remain the question whether, in the numerous successions of teeth which 

 would ensue during the acquisition of the magnitude of Iguanodon Mantelli, the number 

 of serrations might not be increased in greater proportion than the increase of the size of 

 such serrations. That would be the sole modification needed to make them specifically as 

 well as generically the teeth of Iguanodon Mantelli. 



Of the above-described mandibular fossil Mr. Fox writes : — " This jaw was found 

 within a yard of the skull. They were both in a mass of mud that had slided down 

 from the cliff, and was being gradually washed away by the sea." 



What is wanting in the exposed portions of the tooth-germs in the above specimen, 

 viz. the continuation of the marginal serrations, of smaller size, upon the ridge bending 

 from the margin at the broadest part of the crown upon the inner surface of the 



narrowing basal part of the crown, is fortu- 

 nately supplied by an almost entire lower molar 

 of Iguanodon Foxii (PI. II, figs. 12 — 17), which 

 came from a slab of Wealden stone containing 

 a portion of a right mandibular ramus (Woodcut, 

 fig. 1), with the symphysis, s , confined to the 

 lower border of the sloping end (as at 5', fig. 1, 

 PI. I) ; also a few ribs, a caudal vertebra of the pattern of those figured in Pis. VIII and IX 



