TAB. XXI. 

 Plesiosaurus pachyomus, nat. size. 



tig. 



1 . Side view of centrum of dorsal vertebra. 



2. Under view of ditto. 



3. Upper view of ditto. 



4. Upper view of the centrum of a smaller dorsal vertebra. 



•5. A section through the centrum of a small dorsal vertebra, showing the course of 

 the vertical venous canals. 



6. Under view of a caudal vertebra. 



From the Green-sand, near Cambridge. In the Collection of James Carter, 

 Esq., M.R.C.S. 



