A DESCRIPTIVE CATALOGUE 



OF THE 



ARINE REPTILES 



THE OXFORD CLAY. 



PART M. 



Order SAUROPTERYGIA (continued). 



Suborder Plesiosaukia {continued). 



Family PLIOSAURID^E. 



Head relatively large, neck short ; cervical ribs for the most part with double heads. 

 Scapulas not forming an extensive median ventral symphysis ; clavicular arch not well 

 known, but including, in some genera at least, a triangular interclavicle interposed 

 between the inner ends of the ventral rami of the scapulae. Fore paddles smaller than 

 the hind paddles ; pelvis very large. 



Range : Lower Jurassic to Upper Cretaceous of Europe. 



If, as seems probable, the large Rhomaleosaurus (1 Thaumatosaurus) cramptoni is 

 referable to this family, then its range in time was from the Upper Lias to the 

 Chalk, where it is represented by Polyptychodon. The family seems to have flourished 

 especially during the period of the deposition of the Oxford and Kimmeridge Clays. 

 In the Oxford Clay of Peterborough it is represented by three genera : Pliosaurus, 

 Simolestes, and Peloneustes. The genus Thaumatosaurus is very imperfectly known, 

 but if the species Thaumatosaurus victor, recently described by Fraas*, from the 

 Upper Lias of Holzmaden, actually belongs to that genus, it is probably very nearly 



* Palseontograpliica, vol. lvii. (1910) p. 123. 

 PAKT II. B 



