524 BRITISH FOSSIL REPTILES. 



Iguanodon. In giving a description of this tooth (pp. 420, 421, figs, a, h, c, p. 422) 

 before the present discovery of the upper jaw and teeth of an Iguanodon was made, I 

 suggested that it might belong either to Cetiosaurus or Pelorosaurus. I now, however, 

 from its resemblance to the entire premaxillary tooth in the small Iguanodon — as 

 close as is the resemblance in the maxillary teeth — deem it more probably to belong 

 to the larger species and to be a premaxillary tooth of Iguanodon ManteUi ; and I 

 now add two views of this tooth of half the natural size are given in Bin., PL 60, 

 figs. 19 and 20, to facilitate comparison with the magnified view of the laniary of the 

 smaller species (fig. 18). The surface of the crown (fig. 20) which answers to the 

 outer one in fig. 18, and in i, fig. 9, PI. 59, is convex both lengthwise and transversely, 

 and most so in the latter direction along the middle part ; the main or mid-ridge 

 of the maxillary Iguanodoutal teeth being thus represented. On the opposite (inner) side 

 of the crown (fig. 19, PI. 60) the surface is concave across the two thirds next the 

 apex. One margin, the anterior according to the analogy of the small Iguanodon, is 

 convex, the hinder margin along its terminal half is slightly concave. The crown 

 expands antero-posteriorly above the root to nearly midway to the apex, towards which 

 the borders then converge to a point with the different contours above noted. Both 

 borders are trenchant, not serrate. 



Now that we know that a laniariform, or ' lanceolate and acuminate,' premaxillary tooth 

 was associated with molars of the Iguanodoutal type, in a small exemplar of the genus, 

 we may anticipate that the premaxillary part of the skull of Iguanodon ManteUi, when 

 discovered, will show teeth, if they should be preserved there, of the laniary type exempli- 

 fied in p. 422, a, b, c, and in PL 60, 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 (PL 60, 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 {Echinodon), with a corre- 

 sponding type of maxillary dentition (PL 60, 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 Eossil Reptilia of the Cretaceous and Purbeck Strata,' Pal. Soc. vol. for year 

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



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

 iguanodoutal 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 



