260 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. III. 



merit of having first interpreted the characters of this im- 

 portant part of the skeleton, should future discoveries con- 

 firm this view of the subject. 



The gradual transition from the anteriorly convex cervicals, 

 to the plano-concave vertebrae of the posterior dorsal and 

 lumbar regions, appears, at least in the absence of the only 

 certain evidence, a naturally connected spinal column, to 

 warrant the conclusion that all these vertebral elements are 

 referable to the same gigantic herbivorous saurian. 1 



I proceed to point out the most instructive examples of 

 the vertebrae which, according to the present state of our 

 knowledge, are referable to the Iguanodon. 



CONVEXO-CONCAVE CERVICAL VERTEBRA. Wall-case C. 

 The two anteriorly convex cervicals above referred to, are on 

 the upper shelf, immediately to the left of the slab containing 

 six caudal vertebrae, in the lowest compartment of the Case, 

 see the Diagram, ante, p. 227 ;) the small figures in Lign. 

 5, fig. 5, 7, p. 164, may serve to assist the visitor in recog- 

 nising them. They are labelled, " Streptospondylus recentior 

 Ow"* These vertebrae are thus described in my "Geology of 



1 If the discrepancy in the relative proportions and configuration of 

 the cervical, dorsal, and caudal vertebrae, be regarded as presenting 

 objections to this view, let it be remembered that in the spinal column 

 of our domestic Mammalia an equal dissimilarity prevails ; for example, 

 in the Ox, in which the cervical are convex anteriorly, and the convexity 



. gradually disappears in the posterior regions of the spine ; and the 

 bodies of the distal caudals, instead of being solid throughout as in the 

 anterior vertebra, have a large medullary cavity in the centre, as in 

 the fossil reptile, called Poikilopleuron, (ante, p. 166.) Even in the 

 typical form of the genus Streptospondylus, the same disappearance of 

 the convexo-concave character in the middle and posterior dorsals, takes 

 place. See Cuvier's " Oss. Foss.," tome v. p. 156. 



2 These vertebrae are described under another name, (S. major, nob.) 

 together with others from the oolite of Wilts, which unquestionably 

 belong to the genus Streptospondylus,) in "Brit. Assoc. Reports," 1841, 

 p. 88. These vertebrae have therefore now two specific names, one of which 

 must be abandoned ; and are referred to a genus, to which at present 

 their claim is at least very doubtful. " The, coining of names for things 

 glanced at and imperfectly understood, the fabrication of signs without 

 due comprehension of the tiling signified, becomes a hindrance instead 

 of a furtherance of true knowledge" Quoted from Professor Owen on 

 Mr. Bowerbank's Pterodactyle, DIXON'S FOSSILS, p. 404. 



In Cuvier's " Oss. Foss." (tome v.) there are figures of the convexo- 

 concave type from Honfleur. A model of the British oolitic specimen 

 may be obtained of Mr. Tennant, 149, Strand. 



