WEALDEN FORMATIONS. 33 



10 lines; its vertical diameter is 2 inches. The neural arch is, as usual in the 

 present genus, anchylosed to the anterior part of the upper surface of the centrum : 

 one inch and a half of this surface is left free behind the attachment of the arch. 

 The finely wrinkled or fibrous character of the free surface is more strongly marked 

 in these caudal than in the dorsal vertebrae. 



In the three succeeding vertebrse the neural arch diminishes in height, the 

 anterior articular processes diminish in length, and the posterior articular impressions 

 in depth. The upper and lower parts of the sides of the body become somewhat 

 more concave ; the posterior articular surface grows flatter. 



A detached chevron bone, 8 inches in length, consisting of two haemapo- 

 physes, anchylosed only at their distal or inferior extremities, and with their 

 distinct proximal ends more divaricated than are the confluent ones in the Iguanodon, 

 corresponds with the caudal vertebrae here described, and doubtless belongs to the 

 Cetiosaurus hrevis. 



The following are dimensions taken from the four caudal vertebrae above 

 described : 



1st. 



2cl. 



3d. 



4th. 



nches. Lines. 



Inches. Lines. 



Inches. Lines. 



Inches. Lines. 



3 f) 



4 2 



4 3 



4 3 



7 2 



7 1 



6 9 



6 4 



6 10 



6 8 



6 



6 



Antero-posterior diameter of centrum 

 Transverse diameter of centrum . 

 Vertical diameter of centrum 



Of the present species of Cetiosaurus, I have examined specimens of the bodies oi 

 one dorsal and three posterior caudal vertebrae in the collection of Gilpin Gorst, Esq., 

 which were obtained from the central strata of the Wealden, near Battle Abbey, 

 commonly called the " Hastings beds." 



The dorsal centrum closely agrees with those in the Mantellian Collection : 

 its anterior surface is, as in them, nearly flat, or slightly convex; the posterior 

 surface is concave. 



Inches. Lines. 

 The antero-posterior diameter . . . . . .32 



The transverse diameter of the anterior surface . . . ..53 



The vertical diameter of the anterior surface . . . .52 



The neurapophyses, with an antero-posterior extent of base of 2 inches 3 lines, 

 are continuously anchylosed with the centrum, and leave about three quarters 

 of an inch of the posterior part of the centrum free. The floor of the spinal canal is 

 horizontal lengthwise ; its transverse diameter 1 inch 3 lines. 



The posterior caudal vertebrae present an antero-posterior diameter of nearly 

 4 inches, with a breadth of 3^ inches, and a depth of 4 inches, measuring t(j 

 the lower part of the posterior hsemapophysial surface. The antero-posterior length 



5 



