CRETACEOUS FORMATIONS. 11 



receiving the carcases of the dead Plesiosauri, were still in process of formation, 

 where now the dry land of Cambridgeshire has risen. 



In a dorsal vertebra of this species, from the Neocomian deposits of Kursk, the 

 terminal articular surfaces of the centrum were less concave than in the neck, and 

 the lower surface was obscurely or very obtusely ridged. This vertebra measured 

 in : — 



In. lines. 

 Length 19 



Breadth, anterior surface of centrum ....... 2 6 



„ posterior surface of centrum ....... 2 8 



A caudal vertebra of the same species of Plesiosaurus, from the same forma- 

 tion and locality, showed the haemapophysial surface best marked on the posterior 

 border of the centrum ; they were each subtriangular in shape, 6 lines in long 

 diameter, and 1 inch apart. The pleurapophyses were anchylosed to the upper 

 part of the centrum, or over the base of the neurapophysis ; but the sutural line 

 of juncture could be traced. The terminal surfaces of the centrum were mode- 

 rately and gradually concave, but with the broad obtuse border. The lower 

 surface was nearly flat and subquadrate, with only a feeble indication of a rising 

 between two small venous foramina. The length of this vertebra was 1 inch 7 

 lines, the breadth of the centrum was 2 inches 3 lines. a 



I have introduced the above notices of the vertebrae of the Plesiosaurus Ber- 

 nardi from the Green-sand beds of the neighbourhood of Moscow, in illustration of 

 the geographical range of the species at the period of geological time in which 

 it existed ; this period extending from the " neocomian " to the " upper chalk " of 

 the Cretaceous series. In the following section will be found a similar illustration 

 of the geographical range of another Cretaceous Plesiosaur. 



Plesiosaurus neocomiensis, Campiche. Cervical and dorsal vertebra; humerus 



and femur. Plate VI. 



Professor Pictet and Dr. Campiche, in their excellent ' Description des 

 Fossiles du Terrain Cretace des Environs de Sainte-Croix,' 4to, 1858 — 1860, have 

 described and figured three centrums of a dorsal vertebra of a Plesiosaurus, to 

 which Dr. Campiche has attached the name neocomiensis, inasmuch as these fossils 

 were derived from the lower neocomian or " valanginian " beds of the Cretaceous 

 deposits described in the above work. And this name, although there be other 

 neocomian Plesiosaurs, and there may be many, I retain for a species, richly 

 illustrated, from the Upper Green-sand deposits of Cambridgeshire, and which 

 I believe to be identical with Dr. Campiche's. 



