86 REPORT — 1841. 



The neurapophyses, instead of rising and expanding to form a broad plat- 

 form to support the spinous process, as in the Dinosaurian vertebrae of the 

 Wealden, converge rapidly above the spinal canal, and support the spinous 

 and transverse processes by a longitudinal plate not more than from 3 to 6 

 lines in transverse thickness ; from each side of this plate a horizontal, flat, 

 broad, lamelliform transverse process, supported below by a subvertical tri- 

 angular plate, extends outwards and a little upwards ; and a broad, thin, and 

 moderately high spinous process arises, in a peculiar manner, by two laminae, 

 from the whole antero-posterior extent of the ridge-like summit of the neural 

 arch. The fossil is broken in two ; a portion of the centrum adheres to the 

 anterior part of the neural arch, demonstrating the anchylosis of the two 

 parts without trace of suture. In this respect the fossil agrees with Poikilo- 

 pleuron and differs from Iguanodon, in which the neural arch is anchylosed 

 with the centrum, but evident traces of the suture remain, at least in the 

 dorsal vertebrae. The anterior part of the side of- the centrum is impressed 

 by a large surface for the head of the rib ; the surface is concave in the axis of 

 the vertebra, convex vertically, and is bounded above by a well-defined ridge. 



The anterior oblique processes support flat articular surfaces of an ellip- 

 tical form, 16 lines by 9 lines, looking upwards and inwards, their lower edges 

 converging at an angle of 50°. These edges are separated from each other 

 by a fissure 3|- lines broad, continued to the base of the anterior oblique pro- 

 cesses. In the Iguanodon the corresponding surfaces incline to each other 

 at a right angle, and the lower margins of the processes are united by a con- 

 tinuous tract of bone. The present fossil, in the above-cited particular, re- 

 sembles more the Cetiosaurus. Each anterior articular surface is supported 

 by a stout process convex externally, inclining forwards and slightly expand- 

 ing, so as to overhang and extend in a slight degree beyond the anterior end 

 of the centrum : these processes are relatively lower than in the IguuTiodon, 

 in which also they do not extend beyond the centrum : the present fossil, in 

 differing in these two respects from the Iguanodon, indicates characters which 

 are exaggerated in the caudal vertebrae of the Iguanodon. A deep and 

 narrow excavation commences immediately behind the upper and posterior 

 origins of the anterior oblique processes, and is continued backwards, in- 

 creasing in vertical extent, deep into the anterior part of the base of the 

 spinous process. Immediately behind the columnar portion of the anterior 

 oblique process a deep and wide conical cavity sinks, as it were, into the 

 neurapophysis, undermining the anterior part of the base of the transverse 

 process, and dividing the anterior oblique process from the supporting plate 

 of the transverse process. 



The transverse process commences from the summit of the neurapophysis 

 immediately exterior to the anterior part of the base of the spinous process, 

 by a ridge which is continued backwards from the upper and outer margin 

 of the anterior oblique process, in a gentle curve outwards and slightly up- 

 wards. The posterior margin of the base of the transverse process is not 

 continued, in like manner, into the posterior oblique process, but terminates 

 or subsides into a ridge above, and separated from that process by a wide 

 groove. 



The bases of the two transverse processes are only separated from each 

 other, owing to the modification of the neural arch above mentioned, by a 

 thickness of bone not exceeding 4 lines : the interspace of the origins of the 

 two transverse processes in a corresponding vertebra of the Iguanodon 

 measures 4 inches ; the length of the base of the neural arch being the same 

 in the vertebrae compared. 



The antero-posterior extent of the base of the transverse process in this 



