WEALDEN FORMATIONS. 



29 



3 







5 







5 







2 



9 



2 



10 



1 







5 







4 







The following are the dimensions of the best preserved of these vertebrse : 



Inch. Lines 

 Antero-posterior diameter of centrum 

 Transverse diameter 



Vertical diameter .... 

 Height of vertebra to summit of spiae* 

 Antero-posterior diameter of spine 

 Thickness at posterior part of base 

 Heiglit of spine, 1st caudal 

 Heightof spine, 2d caudalf 



The characters and dimensions of these rolled vertebrse of Cetiosaurus from the 

 submarine beds of the Wealden formation, although somewhat obscured by the 

 circumstances under which they are brought to light, are sufficiently satisfactory to 

 establish their generic character, and to give an useful approximative idea of their 

 size and proportions. The corresponding bones from the Wealden of Tilgate Forest 

 supply, by their more perfect state of preservation, the deficiencies of the Isle of 

 Wight specimens, and further establish the co-existence of the Cetiosaurus with the 

 Iguanodon, Hylceosaurus, Streptospondylus, Megalosaurus, and other extraordinary 

 reptiles of that period. The vertebrse of the Cetiosaurus hrevis in the Mantellian 

 Collection are amongst the most gigantic specimens of Saurian remains that enrich 

 it. They include almost entire specimens and bodies of two dorsal vertebrae (Tabs. 

 VIII and IX) and four entire caudal vertebrse, which, if not consecutive, seem to have 

 come not from distant parts of the basal portions of the tail of the s^me individual. 



No. irh " Gigantic vertebra of Iguanodon,''^ MS. Catalogue of Mantellian Col- 

 lection (Brit, Mus.), is a posterior dorsal vertebra of the Cetiosaurus hrevis, and 

 exhibits in a striking manner the peculiar characters of this species, viz., the great 

 depth and breadth, especially the latter dimension (Tab. VIII), as compared with the 

 length or antero-posterior diameter (Tab. IX) of the centrum or bOdy of the vertebra. 



The posterior articular surface (Tab. IX, fig, 2, b) is, in this region of the spine, 

 more concave than the anterior surface, a structure which approximates to that 

 peculiar one which characterises the Streptospondylus. The contour of the articular 

 ends is subcircular, the transverse diameter being somewhat in excess. The centrum 

 is contracted between the two articular ends, is slightly concave in the longitudinal 

 direction at the upper part of the side of the centrum, but deeply concave below, 

 and with a slight indication of a broad, obtuse, longitudinal ridge (Tab. IX, fig. 1, r), 

 along the middle of the concave under surface. In the Iguanodon the sides of the 

 vertebral body are nearly flat in the vertical direction ; in the Cetiosaurus they are 

 strongly convex. The surface at the middle of the vertebra is longitudinally striated 



* This is rounded off, but seems not to have been broken. 



t The 1st and 2d do not here refer to the place of these vertebrje in the tail ; but if the vertebrse were 

 contiguous in the entire animal, the tail must be much shorter than in the Iguanodon. 



