WEALDEN CROCODILES. 399 



Upon the discovery of " opisthocoelian" vertebrae, or those of the " systeme 

 convexe en avant" in the Wealden formations,* I threw out the suggestion! that, as 

 in the second Honfleur Gavial, they might be the anterior vertebrae of a large Wealden 

 Saurian, having vertebrae with flattened terminal surfaces in a more posterior part of 

 the spine. Observing, also, that such vertebrae, in the Cetiosaurus brevis, were slightly 

 concave behind, though flat in front, it seemed to me that this genus might have the 

 best claim to them. But, after pointing out the diflerence in the antero-posterior 

 diameter of the large convexo-concave and plano-concave vertebrae, I remarked that 

 "additional evidence of a very decisive character must be obtained before the great 

 Cetiosaur can be admitted to have resembled the Pterodactyle in such disproportionate 

 length of the cervical vertebrae."} 



No discovery of the long convexo-concave or opisthocoelian vertebrae, so associated 

 with short plano-concave or bi-concave vertebrae, as to have belonged to the same 

 animal, has yet been made, though nearly twenty years of quest and collection of 

 Wealden fossils have passed since the importance of that additional evidence was 

 pointed out. I, therefore, still feel myself without the requisite grounds for a decisive 

 settlement of the question of the genus of the long and large opisthocoelian vertebrae 

 of the Wealden, and continue to refer them, provisionally, as in my ' Report,' to a 

 species of Streptospondylus.^ 



Streptospondylus major, Owen. Pis. 31 and 32 (Crocodilia) . 



The vertebra; so named, in the British Museum, and in that of the late Mr. Saull, 

 F.G.S., now transferred to the Literary Institution, Aldersgate Street, London, have 

 belonged to the region of the neck, or fore-part of the back, and were obtained from 

 the Wealden formation of three localities, viz., Tilgate Forest, in Sussex ; Culver Clifl^, 



* Previous to my Report on British Fossil Reptiles, 'Trans. British Association,' 18-11, these vertebrae 

 had been deemed " proccclian ;" and, in the question of which of the various-shaped Wealden vertebrae 

 might belong to the Iguunodon, Dr. JlintcU thought that " the concavo-conve.ic vertebrae which correspond 

 so entirely to those of the Iguana and Monitor, would seem to offer a more probable approximatioa" 

 (' Geology of the South-east of England') ; only their extreme rarity opposed the hypothesis. 



t ' Report on Brit. Fossil Reptilia,' ib., p. 9(). 



X Ib. 



§ Repoit oil British Fossil Reptiles, 'Trans. Brit. Association,' lS41,p. 91. The futility of subsequent 

 speculations on this subject, in the ' Philosophical Transactions' of 1849, p. 286, has been shown by 

 the discovery of the true cervical vertebra: of the Iguanodon, described in Chapter I of the present 

 Section. 



