WEALDEN DINOSAURS. 523 



The same characters appear, in tlie degree in which the crown is unworn, in the other 

 luaxilkiry teeth. 



In upper or maxilhiry molars of Iguanodon Matitelli the following varieties have been 

 recognised and figured. 



In tlie specimen figured in PI. 23 {Din.), fig. 2, the primary ridge is nearer the fore 

 border of the crown than in fig. 10, PI. 59, of the present species; there is a feeble 

 indication of a secondary ridge on the anterior transversely concave facet. There are two 

 secondary ridges in the posterior facet, and the crown is so worn down as to show no trace 

 of marginal serrations. 



In the upper tooth of lyuanodon ManteUi {Bin., PI. 23, fig. 2, vi), the crown is les8 

 worn than in lyuanodon Foxii, and the marginal serrations appear beyond the line of 

 extreme breadth. The anterior facet shows no secondary ridge ; the two such ridges iu 

 the posterior facet rnn together in the terminal part of the crown. 



In Din., PI. 45, fig. 2, three upper molars are shown in sitil with the Iguanodontal 

 overlap, viz. the hind border of a fore-tooth (m) over the fore-border of the next tooth («) ; 

 in these upper molars the primary ridge is sub-medial, and the front face smooth as in 

 fig. 10, PI. 59 ; the two secondary ridges on the hind facet are feebly indicated. The 

 marginal serrations are shown in the preserved terminal part of the crown, which is 

 entire in the teeth marked n and o. Bisect the tooth n at the line at which it is worn 

 away in figs. 9 and 10, PL 59, and no serrations would appear. In some upper molars 

 of Iguanodon the margino-serrate character is continued in a minute form nearer to the 

 base of the posterior margin. I have figured a left upper molar of this variety in figs. 2, 

 3, 4, of PI. 59 [Din.), and also to show the further variety of three secondary ridges on 

 the hind facet of the crown. 



But the upper molars in the subject of fig. 9 show, as in the enlarged view (fig. 10), 

 a continuation of the relieved or raised lateral borders across the base of the crown, in a 

 curved course, convex toward the fang. This basal ridge does not project beyond the 

 origin of the primary ridge, but falls into that origin. 



I have not observed this character, at least so definitely marked, in any upper tooth 

 of Iguanodon ManteUi, and I regard it as indicative of a specific distinction of the 

 smaller Iguanodon now under review, believing myself entitled to conclude as to its 

 generic relationship fx-om the characters of the dentition of the upper jaw above defined 

 and illustrated. 



It is true that one, at least, of the premaxillary teeth is canine-like. But no portion 

 of the skull of Iguanodon ManteUi has yet been discovered which would supply the means 

 of testing its resemblance to or difference from the smaller species, in regard to this dental 

 character. Consequently, prior to our knowledge of the skull and dentition of the smaller 

 species, the discovery of a tooth answering in size to the ordinary upper molars of 

 Iguanodon ManteUi, but with a lanceolate and acuminate crown, would naturally suggest 

 its reference to some other Dinosaurian genus of the Wealden, of the bulk of the 



