PLESI0SAURID2E. 151 



extremity appears to have been separated by a small va- 

 cuity from that of the distal epiphysis. No history. 



42097. One lateral half of a humerus or femur, with the inner sur- 



face cut; from the Neocomian bone-bed of Potton, Bed- 

 fordshire. The extremity of one epiphysis is entire and 

 detached from the shaft, while a section is shown of that 

 at the opposite end. Purchased, 1870. 



42098. A small imperfect femur, with the proximal epiphysis de- 



tached and lying loose in the cup of the shaft; from 

 Potton. Purchased, 1870. 



Genus PELONEUSTES, Lydekker \ 



Skull and teeth of the general type of Pliosaurus, but the mandible 

 (fig. 47, A) with a longer symphysis, which includes more than a 

 dozen teeth. Neck short, with the anterior vertebras relatively 

 short. Vertebras with the arches and cervical ribs articulating 

 with the centra by suture, of which traces always persist. Cervicals 

 (fig. 55) with very short centra, without distinct haemal ridge, and 



Pr/oiifustcs philarchus. — Ventral aspect of the anterior portion of the pectoral 

 girdle ; from the Oxford Clay of Peterborough. Reduced, om, oinoster- 

 num ; so, scapula; p.cor, ventral(precoracoidal) plate of do. The longitudinal 

 ridge between the ventral and dorsal surface is not sufficiently indicated. 



in the anterior part of the scries with prominent double costal 

 facets, and the external surface smooth ; their terminal faces only 

 slightly cupped, transversely ellipsoidal, and somewhat angulatod. 

 Dorsals with longer centra, having nearly flat terminal faces, and 

 forward overhang of upper part. Pectoral girdle of the general type 

 of Pliosaurus, with a small triangular omostornum between the 

 ventral plates of the scapula) (fig. 48), which have a strong ridge 



1 Quart. Journ. Geol. Soc. vol. xlv. p. 49 (1889). 



