ROOM III. VERTEBRA OP THE IGUANODON. 277 



to the Cetiosaurus brevis, and that last described as corresponding in 

 some respects to the fifth dorsal in the spinal column of the Crocodile, 

 than a diminution in the relief of the buttress supporting the transverse 

 process. In No. 2,115 the neural arch is broken away, and the tract of 

 the centrum left uncovered behind to form the floor of the mtervertebral 

 foramen, is of greater extent than in No. 2,1 33, indicating a more pos- 

 terior situation in the vertebral series. The approach to the quadran- 

 gular form of the body of this vertebra is no proof whatever of a 

 specific and still less of a generic distinction ; otherwise the first sacral 

 vertebra, which is more decidedly quadrate, if found separate, would 

 be equally entitled to a generic value ; but its association, in the sacrum 

 from Mr. Saull's collection, with other vertebral bodies of a very dis- 

 similar character, and with the ilium of the Iguanodon, prevents our 

 falling into an error of such magnitude. We may therefore reasonably 

 conclude, that these vertebrae, to wit, Nos. 2,133, 2,115, belong to the 

 Iguanodon, and that No. 2,115, in the form of the body, approached the 

 first sacral, and was one of the proper lumbar series. 



" The vertebra, No. 2,109, attributed in the above-mentioned report to 

 the (so-called) second species of Cetiosaurus found in the Wealden 

 formation (C. brachyurus), is also a posterior dorsal or lumbar vertebra 

 of the Iguanodon ; the neural arch is much mutilated. The only other 

 element of the skeleton of that species is a caudal vertebra, No. 2,161, 

 which also belongs to the Iguanodon ; being in fact one of the most 

 anterior of the caudal series, and contrary to the character of the 

 genus to which it was referred, it presents one of the most interesting 

 and instructive examples of the rough surface on the sides of the upper 

 aspect of the centrum, left by the removal of the unanchylosed neural 

 arch. The so-called Cetiosaurus brevis being thus founded only on two 

 vertebrae which belong to the Iguanodon, must be expunged from the 

 list of extinct reptiles. 



" The angular posterior caudal vertebrae referred in the Report on 

 British Reptiles, to the Cetiosaurus brevis, I am also inclined to assign 

 to the Iguanodon for the following reasons : Istly, a similar vertebra, 

 as far as can be ascertained, exists in the Maidstone specimen, and in 

 this case an admixture of bones of distinct animals can scarcely be 

 suspected ; 2dly, the numerical ratio of the vertebrae of this kind 

 occurring in the Wealden, to those from the same deposits and localities 

 belonging to other regions of the spinal column, all referable to the 

 Iguanodon, excepting the few megalosaurian and crocodilian vertebrae, 

 is such as long ago to have induced Dr. Mantell to regard them as 

 characteristic of that saurian ; and the occurrence of such vertebrae 

 with those of the sacrum and other bones of the Iguanodon in Western 

 Sussex, described by Cuvier, has already been commented on: 1 3dly, 



1 In reference to the somewhat angular caudals, alluded to in the text, 

 I would remark that with the unquestionable sacral vertebrae of the 

 Iguanodon found at Loxwood, and transmitted to Baron Cuvier by Sir 

 Roderick Murchison, (ante, p. 269,) there were several that appeared to 

 belong to the same individual, which possessed the angular form and 

 sulcated base of the bones described in the text, as may be seen by 



