﻿WEALDEN FORMATIONS. 



3 



(it)., figs. 5, 6, 7) are taken from teeth of the same individual as that to which belonged 

 the mandible (fig. 1) and the bones of the fore-foot described in 'Supplement,' No. IV. 



I am indebted to A. J. Hogg, Esq., for the opportunity of examining and figuring 

 the instructive specimen (PI. I, fig. 8). It was discovered in the hard limestone, locally 

 known as the " Under Feather," which is situated from four to five feet below the accumu- 

 lation of shells of Ostrea distorta, called the " Cinder Bed," in the Middle Purbecks. 



A reference to p. 22, fig. 4, of my ' Monograph on the Fossil Mammalia of the 

 Purbeck Formations, British Mesozoic Mammals ' (Palaeontographical Society, vol. xxiv, 

 issued for 1870), will show the position of the Middle Purbeck series in which the 

 present interesting evidence of the Iguanodon was entombed. It is the first example of 

 that genus, to my knowledge, from the Purbeck series. 



In making this statement I refer, of course, to the unequivocal evidence of Iguanodon 

 afforded by the dentition. A large phalangeal bone is figured by Buckland in PI. XLI, 

 ' Geological Transactions,' Second Series, as a " metacarpal " of Iguanodon. It was 

 picked up "on the sea-shore, about half a mile north of the village of Swanwich " (ib., 

 p. 428), and though "more or less injured by rolling on the sea-shore" has most claim 

 to be referred to the hind-foot of the Iguanodon. It was most probably washed out of 

 the cliffs of iron-sand and sandy clay described by Webster as dividing the Greensand 

 of Ballard Down from the upper body of the Purbeck " limestone.'' 



The portion of jaw here exposed (PI. I, fig. 8), is the dentary element of a right 

 mandibular ramus, about the size of the Stammerham specimen (Monogr. cit., vol. for 

 1854, Plates XI, XII), but is mutilated at both ends ; it includes, however, in an 

 alveolar tract of four inches, ten teeth, alternately young and old. The foremost, b, is a 

 lanceolate and acuminate crown-germ, least advanced in size and lowest in position in the 

 jaw. The second, a, is fully in place with the upper third of the crown worn away 

 and supported by a long, slender, tapering fang, occupying the interspace between the 

 first and third teeth. The latter shows the crown fully formed, with the apex risen 

 almost to the level of the worn surface of the antecedent tooth, between which and the 

 fourth it accurately fills the interspace. The fourth tooth, a, rises to a higher level than 

 the second and has rather more of the crown worn away ; much of its narrow fang is 

 exposed. The. crown of the fifth tooth— third of its series, ^ — fills, like the third tooth 

 — second of the series b— the interval between the fangs of the fourth and sixth teeth. 

 The sixth tooth rises a little higher than the fourth, and is rather more worn. The 

 seventh tooth— fourth of the scries b— is more complete and rises higher than the fifth 

 or third ; the apex of its crown is on a level with the worn surface of the sixth tooth : the 

 outer part of the lower half of the crown and beginning of the fang of the seventh tooth 

 has been broken away, showing the pulp-cavity in the latter. The eighth tooth— fourth of 

 the series, a— is worn down to the contracted base and beginning of the fang. The ninth 

 tooth has risen above it, has come into service, and the crown is supported by a strong 

 root. Beyond this is part of the crown of a successional tooth of a third series, c. 



