264 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. III. 



tive length of a vertebra must always be taken exclusively of 

 the articular convexity, whether that be in front or behind, 

 as is the practice in stating the absolute length of the spine 

 or of its individual regions. Deterred by the great length of 

 the cervical vertebrae referred to the Streptospondylus major, 

 when compared with the shortness of the dorsal or lumbar 

 vertebne assigned by him to the Cetiosaurus brevis, Professor 

 Owen was unwilling to associate them together as belonging 

 to the spinal column of the same species of reptile, which, 

 however, appears to be really the case, as I shall afterwards 

 have occasion to demonstrate." 1 



If Professor Owen's opinion be correct, and the bones in 

 question belong to the Streptospondylus, then the vertebrae 

 composing the neck of the Iguaiiodon are at present un- 

 known. 



The only specimen that appears to me to afford conclusive 

 evidence on this question is in the possession of J. S. Bower- 

 bank, Esq. F.R.S., and consists of a considerable portion of 

 the spinal column of a very young Iguanodon, imbedded in 

 calciferous grit. Found with this fossil, but detached from 

 it, and without any indication of its connexion with the spine, 

 to which, I believe, it unquestionably belongs, is a series of 

 three cervical vertebrae, which, with his characteristic libe- 

 rality, Mr. Bowerbank allowed me to figure in illustration of 

 my fourth Memoir on the Iguanodon, in "Philos. Trans.," 

 18,49. PI. XXIX. fig. 9. 



These vertebrae are especially instructive because they de- 

 monstrate the true characters of the bones of the neck in a 

 very young Iguanodon ; for it is to this reptile this verte- 

 bral column must be ascribed. Unfortunately, the bodies of 

 the vertebrae have been crushed and compressed almost flat 

 laterally, and the natural form of the inferior part of the 

 centrum is destroyed, the visceral aspect presenting a sharp 

 ridge, and thus assuming a different contour to that of an 

 adult cervical in my cabinet, which has been compressed in 

 an opposite direction. Nevertheless, the close analogy be- 

 tween these vertebrae is sufficiently obvious ; the structure of 



1 In confirmation of the remarks of Professor Melville, I may add 

 that among the large convexo-concave saurian vertebrae recently obtained 

 from the strata of Tilgate Forest, are cervicals and dorsals, belonging to 

 two, if not three, distinct generic types. 



