WEALDEN IGFANODONT AND OTHER DINOSAURS. 4 / 



dorsals approximate, however, to those of an unnamed Iguanodon 

 in the Museum from near Hastings ; and the absence of teeth like 

 those of Trachodon in the Isle of Wight tends, as far as it goes, to 

 indicate that Sphenospondylus agreed in dental character with 

 Jguanodon. That we should find in England a form more or less 

 intermediate between Trachodon and Iguanodon is, however, to be 

 expected from the occurrence in this country of a Dinosaur which I 

 provisionally refer to the former. This determination is based on 

 a tooth from the Cambridge Greensand (B. M. No. E. 496), figui-ed 

 by Sir R. Owen in his ' Cretaceous Reptilia ' (Mon. Pal. Soc), 

 suppl. ii. pi. 7. figs. 15, 16, under the name of Iguanodon Mantelli ; 

 but which, as Prof. Seeley has pointed out on page 591 of vol. xxxv. 

 of the Society's Journal, agrees so closely with the teeth of Leidy's 

 Trachodon FoidJd, from the Upper Cretaceous of ]N"ew Jersey, that, 

 in the absence of any evidence to the contrary, I propose to refer 

 it provisionally to that genus, with the name of T. cantabrigiensis *. 

 This tooth exhibits the peculiar groove on the inferior side of 

 the root made by the point of the tooth immediately below, which 

 is so characteristic of the genus. Pinally, since Prof. Seeley 

 has not applied a specific name to the type of S^henospondylus, I 

 propose that it should be known as S. gracilis. 



Turning to Iguanodon Preshvichi — the type of Cumnoria — which 

 in the structure of its sacrum diff'ers very widely from the typical 

 forms, there is much to be said for the view expressed by Prof. 

 Seeley as to its right to generic distinction ; but, after having been 

 for some time inchned to adopt this view, I think on the whole 

 that it is better to retain it in the original genus, of which it will 

 form the type of a very distinct group. The pelvis is unfortunately 

 very imperfectly known, all that can be definitely predicated being 

 that the preacetabular process of the ilium is considerably elongated. 

 In the structure of the sacrum this form agrees very closely with 

 the North- American Upper Jurassic genus Camptosaurus, Marsh f, 

 in which the ilium is remarkable for the great reduction of the 

 preacetabular process, the pubis is of equal length with the ischium,, 

 and the latter is stouter and shorter than in Iguanodon, the two 

 latter features being also found in Hyjpsilophodon. 



The first of the Iguanodont specimens from the Wadhurst Clay 

 that I propose to notice comprises a part of an associated skeleton 

 including the left ilium, the acetabular region of the pubis of the 

 same side, a number of more or less imperfect dorsal, lumbar, and 

 caudal vertebrae, the proximal half of a tibia, and two metatarsals ; 

 besides some imperfect bones which it is difiicult or impossible 

 to determine. Of the vertebrae, one of the most perfect from that 

 portion of the dorsal region where there is a rib-facet distinct 

 from the transverse process, is represented in fig. 1. The Iguan- 



* The vertebra from the same formation described on p. 613 of the above 

 cited paper under the name of Eucercosaurus, being unlike those of Trachodon ^ 

 are not likely to belong to this form. 



t Amer. Journ. Sci. ser. 3, yol. xviii. p. 501, pi. iii. (1879). Here named 

 Camjptonotus, but subsequently amended. 



