﻿WEALDEN FORMATIONS. 



15 



From the above facts I conclude that the fossils discovered by Mr. Fox, and figured 

 in Pis. I and II of the present Monograph, afford the much-needed exemplification 

 of the cranial structure in the genus Iguanodon, and that they contribute to supply 

 characters of the serrident family of Dinosauria which were not given in the fossil skull of 

 Scelidosaurus Harrisonii, figured in Pis. V and VI of the Monograph on that Liassic 

 Dinosaur, Pal. Soc. vol. for year 1859. The importance of this addition to the knowledge 

 of Dinosaurian structures induces me to recapitulate and enforce the passing remarks, 

 offered in the course of my descriptions, on statements which, if true, would leave such 

 addition still a desideratum. 



Serrations of the free edge of the crown, affirmed to be " so characteristic of the teeth 

 of Jguanodon " (Huxley, ut supra, p. 5), are not in any degree characteristic of that genus. 

 They are present in the teeth of older Dinosauria as of contemporary genera. The 

 Liassic Scdidosaur and the Purbeck Echinodon alike manifest the modification. The true 

 generic dental characteristic of Iguanodon is the superaddition to marginal serration of 

 ridged and grooved sculpturing of one of the surfaces of the crown of the teeth ; to wit, 

 the outer one in the upper teeth, the inner one in the lower, the sculpturing being in so 

 broad and definite a style that the ridges can be defined and distinguished. This 

 character, combined with marginal serration, in the molars of the small Dinosaur in 

 question, and this other character of the overlap of the expanded crowns in the one 

 direction above described, are now submitted to impartial Taxonomists as the ground of 

 the reference of the subject of the present section (§ 2) to Conybeare's genus. 



So singular an anomaly in the arrangement of a molar series, as the reversal of the 

 order of overlapping at its two extremes might well support a generic distinction, but 

 would need clear and indisputable demonstration for acceptance. Iguanodon Foxii 

 affords no real ground for the ascription of such an anomaly. 



As little does the fossil discovered by Mr. Fox support the assertion that its teeth 

 have " no trace of the serrations on the free edge of their crown." 



Prof. Huxley seems at one time to have been open to the evidence of the true 

 character of the teeth in the unique skull from the Isle of Wight Wealden. But its 

 discoverer had expressed his belief 1 that it might belong to a young Iguanodon, or to a 

 new small species of that genus ; — like the skeleton in which I had previously pointed out 

 Iguanodontal characters. 3 So, in 1869, Prof. Huxley writes :—" A more critical com- 

 parison, however, has convinced me that the teeth of this reptile are perfectly distinct 

 from those of the great Wealden Dinosaurian " {ut supra, p. 6). My own scrutiny, made in 

 no critical spirit, but simply to find out the true state of the case, leads me to affirm these 

 teeth to be specifically distinct, but not generically, from those of Iguanodon Mantelli. 

 What the meaning of his term « perfectly ' may be, as predicated of this distinction, the 

 author quoted nowhere defines. 



1 ' Proceedings of Sections, British Association,' Norwich, 1868. 



2 ' Monograph on the Fossil Reptilia of the Wealden and Purbeck Formations— Dinosauria (Igua- 

 nodon),' Palceontographical Society's volume for year 1854, p. 2, PI. I. 



