﻿SUPPLEMENT (No. V) 



TO THE 



MONOGRAPH 



ON 



THE FOSSIL EEPTILIA 



OF 



THE WEALDEN AND PURBECK FORMATIONS. 



(IGUANODON.) 



§ 1. Mandible and Mandibular Teeth. Plate I, figs. 1, 8. 



The dentary element of the right mandibular ramus of the young Iguanodon 

 (' Monograph on Wealden Reptilia, Binosauria, Iguanodon/ part, ii, Plates XI, 

 XII), 1 discovered in the Wealden of Stammerham, near Horsham, Sussex, by G. B. 

 Holmes, Esq., demonstrated the fact that the sculptured surface of the crown in the 

 teeth of the lower jaw was turned inward, the smooth surface outward, toward which 

 aspect the entire tooth was moderately bent. Moreover, the alveoli in that jaw showed 

 eighteen teeth to be the number supported in a close-set series and working position in 

 the dentary element (ib., ib., p. 22). 



The portion of mandible obtained by S. H. Beckles, Esq., from the locality of the 

 limb-bones described in ' Supplement ' No. IV, 2 is also the dentary element of the right 

 ramus, of which a figure of the inner side is given in Plate I. On this surface the 

 crowns of seven teeth nearly risen into place are seen ; the worn crown and fang of a few 

 of the preceding generation of teeth {a, a) have been preserved, and the summits of the 

 crown of a few teeth of a third set (c) in succession are seen in the interspaces of the 

 more developed teeth of the second set {b, b). 



The length of the portion of mandible here preserved is eighteen inches; that of the 

 corresponding part of the mandible of the Iguanodon discovered by Captain Brickenden 

 in the Wealden of Tilgate (ib., ib., PI. XIII) measured 20 inches. It is probable, 

 therefore, that Mr. Beckles' specimen had nearly attained the full average size of the 

 great herbivorous reptile. 



The anteroposterior breadth of the teeth rising into place averages 9 lines ; the 

 largest mandibular teeth of Iguanodon (ib., ib., PI. XVIII, figs. 3, 3 a) give 1 inch 

 ' Pal. Soc. Vol. for year 1854. ' Ibid. 1871. 



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