406 BRITISH FOSSIL REPTILES. 



genus were first founded* by the shortness of their antero-posterior diameter as 

 compared with their breadth and depth, whence I proposed to designate the species by 

 the name of Cetiosaurus brevisA 



The centrum of a dorsal vertebra of this species from Culver Cliff measures, 



luch. Liues. 

 in autcro-posterior diameter . . . . . .36 



transverse diameter . . . . . . .64 



vertical diameter . . . . . . .60 



The hind articular end (PI. 34, fig. 2, b) is moderately concave : the front end (ib., o) 

 from the wearing away of the margins, appears slightly and unevenly convex. The 

 contracted middle part of the vertebra is concave lengthwise, and pretty I'eguiarly 

 convex in the direction transverse to the axis of the vertebra : the free surface is finely 

 striated, and perforated here and there by vascular foramina : there is no lateral 

 depression. The bases of the neurapophyses, instead of having their long diameter 

 corresponding with the axis of the vertebra, as in Iguanodon, present it in the direction 

 transverse to that axis, as in Plesiosaurus : they do not quite meet at the middle of the 

 upper or neural surface of the centrum, but are there divided by a narrow longitudinal 

 tract forming the lower part of the spinal canal. The antero-posterior extent of the 

 anchylosed base of the neural arch (ib., ») is 2 inches 6 lines : the transverse diameter 

 of the arch is 5 inches. 



The caudal vertebra of the same species, also from Culver Cliff, present the same 

 length and unequal concavity of the articular extremities ; the anterior one, here 

 determinable by the anterior position of the narrower hsemapophyses, being the 

 deepest : the sides of the body are more compressed, and more convergent towards 

 the under surface ; so that, as the expanded margins of the articular ends are worn away, 

 the centrum presents rather a triangular than a subcircular contour. The dis- 

 proportion of its antero-posterior with its transverse and vertical diameters, 

 distinguishes it from the caudal vertebrae of the Iguanodon. The neurapophysis rises 

 from the anterior three fourths of the centrum, and sends forward a subprismatic 

 anterior oblique process, but does not develope a posterior one : it then contracts, and 

 inclines to the base of the spine, which is much shorter than in the Iguanodon. The 

 spinous process inclines backward from the vertical axis of the centrum at an angle 

 of 45°. A short transverse process is developed from the junction of the neur- 

 apophysis with the centrum. The ha?mapophysial surfaces appear single on both the 

 anterior and posterior parts of the lower surface; they are nearly flat, and slope 

 towards each other. 



* See ' Proceedings of the Geological Society' for June, 1841. 



t ' Report of British Fossil Reptilia," lb4I, ' Trans. Brit. Association,' p. 94. 



