172 satjkopterygia. 



Genus non det. 

 (Plesiosaurus ellipsosjoondylus, Phillips \) 



Very imperfectly known ; of large dimensions. Cervical vertebrae 

 with short centra, having transversely ellipsoidal and slightly 

 cupped terminal faces, with single costal facets, and the costo-central 

 suture persistent. 



Hab. Europe (England). 



31916. The centrum of a cervical vertebra; from the Kimeridge 

 Clay of Shotover, near Oxford. Length 0,066 (2*6 inches), 

 width 0,096 (3-8 inches), height 0,076 (3-0 inches). 

 These dimensions accord very closely with those of the 

 largest cervical described by Phillips. The suture between 

 the rib and the centrum is very apparent. 



Purchased. About 1852. 



Genus POLYPTYCHODON, Owen 2 . 



Syn. Lutkesaurus, Kiprijanoff 3 . 



Skull imperfectly known, but relatively large and of moderate 

 elongation. Teeth (fig. 58) large and stout with conical crowns, 

 marked by a number of prominent vertical ridges on all sides. Neck 

 probably short, with the anterior vertebras large. Cervical vertebras 

 with centra of medium length, having the terminal faces flattened, 

 with a sinuous profile caused by the overhang of the upper border 

 of the anterior face and the prominence of the lower border of the 

 same ; costal facets single, and neural arch and cervical ribs anchy- 

 losed to centrum. Dorsals 4 with the same forward overhang of the 

 upper part of the centrum, and a mammilla in the centre of the 

 terminal faces. Pectoral and pelvic girdles unknown. The limb 

 referred by Kiprijanoff to the so-called Lutkesaurus agrees very 

 closely with that of Cimoliosaurus jportlandicus. 



This genus is probably derived from Cimoliosaurus, with which 

 it agrees in the general structure of the teeth and vertebras. 



1 Geology of Oxford, p. 372 (1871).— Ex Owen, MS. 



2 Odontography, pt. ii. pi. 72, figs. 3, 4 (1841). 



3 Mem. Ac. Imp. St. Petersbourg, vol. xxxi. art. 6, p. 35 (1883), 



4 See Seeley, Quart. Journ. Geol. Soc. vol. xxxii. p. 433. 



