﻿WEALDEN FORMATIONS. 



9 



we may anticipate that the premaxillary part of the skull of Iguanodon Mantelli, 

 when discovered, will show teeth, if they should be preserved there, of the laniary 

 type exemplified in PI. II, figs. 18, 19, and 20. The anterior mutilation of the 

 skull of the Scelidosaurus, with maxillary teeth having the terminal and more expanded 

 half of the crown serrate (PI. II, fig. 21), precludes, at present, the determination 

 whether the iguanodontoid molars of this genus were similarly associated with anterior 

 laniaries. But the dentition of the small Purbeck Dinosaur (Ec/rinodon) , with a corre- 

 sponding type of maxillary dentition (PI. II, fig. 22), does include one or more laniaries in 

 advance of molars of the serrate type, as in the small and large Iguanodons (' Monograph 

 on the Fossil Reptilia of the Cretaceous and Purbeck Strata,' Pal. Soc. vol. for year 

 1858, p. 35, PI. VIII, figs. 1, 1 a). 



I next proceed to determine how far the dentition in the small skull repeats the 

 iguanodontal character of overlapping arrangement of the crowns of the teeth. 



The right tympanic and mandibular ramus are wanting in the fossil. The left 

 mandibular ramus has been pushed obliquely to the right side, and its fore end has 

 partly displaced the first and second molars, beyond which the projecting end has 

 been broken away. The crowns of those teeth, so driven out of line, are thereby 

 partly withdrawn from their sockets, so as to expose the basal half of their fangs. 

 From this I infer that the force has operated upon the recent animal : for, if it 

 had acted subsequent to fossilisation, through movement of the matrix, it would 

 have broken the teeth, at that time cemented to their sockets. Howsoever that may be, 

 displacement is obvious, and no inference can be drawn as to the original relative position 

 of the crowns of these anterior teeth. As it is, the anterior edge of the crown of the 

 third molar does not overlap in the slightest degree the posterior edge of the crown of 

 the tooth before it ; the reverse is the case if any overlap at all can be predicated. 1 In 

 the undisturbed molars the hind edge of each tooth projects a little beyond the fore 

 edge of the one behind it. This is the characteristic arrangement of the upper or 

 maxillary teeth of Iguanodon. It is exemplified in the specimen figured in my second 

 ' Supplement ' to the Monograph on the genus (Palseontographical Society's volume for 

 1858, issued 1860), PI. VII, fig. 2, in the undisturbed upper teeth, there marked m , n, o. 

 The overlap by the anterior edge of the crown in the anterior four maxillary teeth of the 

 posterior edge of the tooth in front, and the reverse arrangement in the rest of the 

 maxillary series, where " the overlap seems to have taken place in the opposite direction/' 

 may be a character of Hj/jmlop/iodon, Huxley, but is certainly not a character of the 

 present nor of any previous evidences of Iguanodon. In the small species discovered by 

 Mr. Fox, as in the large type of the genus, the maxillary grinders not merely seem to 

 overlap, but do so, in the way and degree exemplified iu fig. 9, PI. I, and in fig. 2, PI. 

 VII, of the former Monograph, above cited (Pal. Soc. vol. for year 1858), on the Iguanodon. 



1 "The anterior four teeth are rather smaller than the others ; and this is especially true of the first 

 tooth. The anterior edge of the crown of each of these teeth slightly overlaps the posterior edge of the 

 crown of its predecessor." — Huxley, loc. cit., p. 5. 



