BRITISH FOSSIL REPTILES. 77 



mined are from the lias of Street and the neighbourhood of Bath ^ 

 also from the lias of Bitton, in Gloucestershire ; and from that 

 of Charlton, two miles from Cheltenham. I have not yet ob- 

 served specimens from the lias of Whitby. 



None of the Plesiosaurian vertebrae of the Wirtemberg lias 

 bone-beds can be referred to the present species. 



I have next to notice some vertebrae of a Plesiosaurus contained 

 in the Museum of the Philosophical Institution at Bristol, which 

 approximate to the character of the last-described species in 

 the prominence of the costal articular surfaces, but which differ 

 in the shape of the body in so marked a degree as to render in- 

 admissible the idea of their specific identity. In the PL arciia- 

 tiis the contour of the articular surface is nearly circular, with 

 a narrow superior emargination corresponding with the canal 

 for the spinal marrow : in the present species the contour of 

 the same part approaches to the triangular form from the flat- 

 ness and upward convergence of the upper moiety of the sides 

 of the body. 



The anterior and posterior- articular surfaces are flatter, but 

 exhibit a slight middle convexity. 



The inferior surface is traversed by a broad longitudinal 

 elevation, on each side of which is the typical foramen. From 

 the median ridge the surface of the vertebra extends in a slight 

 concave curve to the base of the transverse process, the antero- 

 posterior extent of which equals one half of that of the centrum 

 itself. 



The base of the neurapophyses is bounded by a gentle convex 

 line, and the extent of surface intervening between it and the 

 costal articular surface exceeds by one half the vertical diameter 

 of that surface. 



The upper part of the neurapophyses, and their spine, were 

 broken off in the vertebrae examined by me, the only ones of 

 this species which I have as yet seen. 



The length of the body of the cervical vertebrae here Inches. 



described is 3^ 



Its transverse diameter, including transverse processes 4|- 

 Its vertical diameter '6^ 



Localities. — The vertebrae here described are from the lias of 

 Weston, near Bath*. 



* In Professor Sedgwick's collection at Cambridge there is a cervical verte- 

 bra oi a. Plesiosaurus, measuring two inches and a half in transverse diameter, 

 having the neurapophyses anchylosed to the centrum, and the ribs to the 



