CRETACEOUS FORMATIONS. 109 



both in length and breadth. The platform is chiefly supported by a buttress-like 

 ridge, which rises nearly vertically from the hinder and outer angle of the base of the 

 neurapophysis, and gradually expands as it ascends, inclining a little forwards to blend 

 with the under part of the overhanging platform. A transverse process, p, answering 

 to the lower one or " parapopliysis" in the vertebra of the Crocodile (T. V, fig. 3,p,)* 

 extends from the side of the neurapophysis anterior to the buttress ; its base presenting 

 the form of an oval with the long axis vertical, and the small end upwards from which 

 a smooth, convex prominence extends upwards and forwards, and subsides on the base 

 of the anterior zygapoplrysis, which is developed from, or terminates, the fore-part of 

 the neural platform. This transverse process is very short, and afforded an articular 

 surface for the head of the rib. The second transverse process, answering to the 

 upper one or " diapophysis" in the vertebra of the Crocodile [d, T. V, fig. 3)f which 

 has been broken away in this specimen, is better preserved in the vertebra nearest the 

 upper border of the slab in the T. XXXIII, and in a few other detached vertebrae. 

 The anterior zygapophyses scarcely project as distinct processes from the neural 

 platform, but seem to form the natural anterior boundary of that part ; their thickness 

 gradually diminishes to an edge anteriorly, and their flat oval articular surfaces look 

 obliquely upwards and inwards. The posterior articular surfaces are developed from 

 the under and back part of the neural platform, and look downwards and outwards, 

 over-hanging the hinder surface of the centrum. This part of the neural arch has 

 been somewhat crushed and depressed in the vertebra which best shows its characters 

 amongst those in Mr. Bensted's specimen ; but one may see that the plane from which 

 the neural spine rises has sloped from behind downwards and forwards. The base of 

 the neural spine is coextensive with the neural platform ; from the middle line of which 

 it rises, but it contracts as it ascends, and inclines backwards ; its height is shown to 

 equal that of the rest of the vertebra in one that lies between the humerus and femur ; 

 although it has there suffered fracture ; in the other specimens the broken summits of 

 the spines have not been preserved. 



In the characters above defined we may plainly recognise a vertebra differing 

 from any of those that have been previously described ; from those of the Crocodiles 

 and Gavials (T. IV, V, IX, and X)| in the flattened articular ends of the centrum; 

 and by the same character from those of the Ophidian (T. XIII and XIV), § and 

 Lacertian (T. VIII, IX, and X) || reptiles which we have hitherto met with in the 

 Tertiary and Cretaceous deposits ; it is equally distinct from the biconical and short 

 vertebrae of the Ichthyosaurus (T. XXII). Were the centrum of the Iguanodon's 

 vertebra (T. XXXV) to be found detached from the neural arch, it might not be so 

 easy to distinguish it from that of a dorsal vertebra of a Plesiosaurus, which is similarly 



* Monograph on the Reptiles of the London Clay, pp. 33 — 36. t Op. cit. 



X Monograph on the Reptiles of the London Clay, Part ii. § lb. 



|| Monograph on the Reptiles of the Cretaceous Formations. 



