﻿WEALDEN FORMATIONS. 



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[Appendix to Supplement No. V Monograph on Iguanodon Foxii, Ovv.] 



Since the foregoing pages went to press, and long since the plates were completed and 

 printed off, some additional observations have been recorded on specimens acquired from 

 Mr. Fox's locality, which have been adduced in support of the title of my Iguanodon Foxii 

 to generic distinction. The most important and decisive is that of my experienced fellow- 

 contributor to the Monograph of the Palaeontographical Society, Mr. Boyd Dawkins. 1 

 Ilypsilophodon, it appears, has seven digits in each fore-foot, and five developed ones on 

 each hind-foot, whilst Iguanodon has but five digits on each fore-foot (' Monogr. Wealden 

 Reptilia/ Supplement No. 4 2 {Iguanodon), 1S72, PI. Ill), and three developed digits on 

 each hind foot (lb. ib., Supplement No. I 3 {Iguanodon), 1858, PI. I). He justly, there- 

 fore, cites the distinction between Hipparion and Equus as warranting, or " sufficient for," 

 the adoption of the same taxonomic distinction between Hypsilopliodon and Iguanodon, 

 It was unnecessary to remark (as the learned Society addressed by Mr. B. D. well 

 knew) that two additional developed toes, with hoofs, are present in both fore and hind 

 feet of the Miocene Horse, which toes are represented by splint-like rudiments of the meta- 

 podial elements in Pliocene and Modern equines, like the digit I in the above-cited plate 

 of the Iguanodon's foot-skeleton. 



Other observations, by Mr. Hulke, have not the same weight as those on the shape of 

 the unequal phalanges of the fore- foot, 4 with me as those of Mr. Boyd Dawkins, seeing 

 that some of the sacral vertebrae of the Iguanodon, those, e.g. marked s 4 and s 5 in the 

 specimen of sacrum figured in PL III of my « Monograph on Wealden Reptilia,' Part II 5 

 {Iguanodon), 1855, "are cylindroid and rounded below." 6 Such character might well be 

 extended in a smaller species, but would not lead me to found thereon a generic distinc- 

 tion and name. 



Moreover, in the series of eight vertebras of which " the three last are firmly anchy- 

 losed, and the seventh and eighth form part of the sacrum," Mr. Hulke admits that 

 " they are constricted in the middle, and their transverse processes, which spring from 

 the junction of two vertebras, are bent backwards, joining the dilated outer end of the 

 transverse processes of the next vertebra, including a large subcircular loop." 7 This 



1 "Proceedings of the Geological Society of London,' 5 No. 273, November 19, 1873, 8vo (p. 2 of 

 'Abstracts'). 



2 Palseontographical Society's volume for year 1871. 3 Volume for year 1856. 

 4 ' Quart. Journ. Geol. Soc.,' No. 1 16, June 25th, 1873, p. 528. 5 Volume for year 1854. 

 6 Proceedings, Nov. 19th (' Abstracts,' p. 2). 7 lb., ib., p. 1. 



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