PLEST0SAUR1D.E. 



157 



fibula : length 0,076 (3-0 inches), width 0,079 (3-1 inches) ; 

 the homology of these bones being determined from com- 

 parison with the skeleton of Plesiosaurus rostratus. 



Presented by F. W. Crick, Esq., 1888. 



47411. The entire mandible ; from the Oxford Clay of Peterborough, 

 (Fig.) Northamptonshire. The teeth are wanting; but one or 

 two germs are seen in the alveoli. This specimen (wood- 

 cut fig. 47, A.) is noticed by the writer, Quart. Journ. Geol. 

 Soc. vol. xlv. p. 49, and also in the ' Eec. Geol. Surv. Ind.' 

 vol. xxii. p. 50. There are seven enlarged dental alveoli at 

 the anterior extremity of the symphysis. 



Sharp Collection. Purchased, 1876. 



4635 4. A tooth, in matrix ; from the Oxford Clay of Christian- 

 Malford, Wiltshire. This specimen cannot be distin- 

 guished from the smallest upper tooth of No. li. 1253. 



Cunnington Collection. Purchased, 1875. 



Fig. 55. 



Peloncustes philarchus. — Posterior and right lateral aspects of an imperfect cer- 

 vical vertebra; from the Oxford Clay of Peterborough, co, rib. £. 



R. 1254. Cast of the centrum and base of the arch of a cervical 

 vertebra. The original (fig. 55) belongs to the type 

 skeleton, which was obtained from the Oxford Clay of 

 Peterborough, and is preserved in the Woodwardian 

 Museum at Cambridge. It is described by Seeley in his 

 ' Index to Aves &c. in the Cambridge Museum,' p. 139, 

 and belongs to an adult individual. The ribs are- anchy- 

 losed to the centrum, but show an imperfect division 

 into two heads. The posterior faco has been some- 

 what crushed in, and its contour is probably altered by 

 pressure. In profile there is a forward overhang of the 

 upper part of the centrum, and there is a descending pro- 



