BOOM III. CERVICAL VERTEBRAE OP THE IGUANODON. 263 



in such collocation with other well-determined bones and 

 vertebrse of the Iguanodon, as to leave no reasonable doubt of 

 their belonging to that animal. 



othly, The number of these vertebrse of different ages and 

 sizes in our collections is such as we might have expected on 

 that supposition ; and 



Gthly, if these be not the cervical vertebrae of the Igua- 

 nodon, we have the (assumed) Streptospondylus major with 

 nothing but a neck, whilst the Iguanodon, as yet known, 

 is wholly destitute of that region of the spine. Is it not, 

 therefore, more probable that the neck of the so-called Strep- 

 tospondylus belongs of right to the Iguanodon, especially as 

 the bones of that reptile, tested by the fortunate discovery of 

 the Maidstone specimen, constitute the great majority of the 

 osseous relics from the deposits of the Weald 1 ? in other 

 words, the Iguanodon is the reptile par excellence characteristic 

 of the Wealden formation. 



"The Streptospondylian form of the body of a vertebra- 

 can no more characterize a genus of Keptiles than the am phi - 

 ccelian or ccelospondylian modifications ; each is common to 

 a group of species constituting not only distinct genera and 

 families, but also orders and subclasses. Nay, the Strepto- 

 spondylian type is not even persistent throughout the elements 

 of the same spinal column ; it disappears towards the middle 

 of the dorsal region in the Steneosaurus rostro^ninor, the best 

 known example of this structure, and that in which it was 

 first recognized by Baron Cuvier. The genus /Streptospondylus 

 of V. Meyer ought therefore to be abolished, and the residual 

 generic application Steneosaurus (G. St. Hilaire) be retained 

 to designate Cuvier's first Gavial of Honfleur. The amphi- 

 coelian and procoelian forms are generally continued through 

 the whole length of the vertebral column ; the Streptospon- 

 dylian modification in the last sacral replaces, and in the first 

 caudal is superadded to, the proccelian form of the vertebral 

 bodies characteristic of the living Crocodiles. 



" In the Report on British Reptiles much stress is laid on 

 the uniformity in length of the bodies of the same vertebral 

 series in Reptiles ; this indeed holds good within certain 

 limits among the less complicated smaller existing Lacertee, 

 but will lead us into error if rigidly applied to the more 

 highly organized extinct Saurians and Crocodiles. The rela- 



