Jll 



PLAGIOSTOMA Hoperi. 

 TAB. CCCLXXX. 



Spec. Char. Transversely ovate, oblique; 

 valves convex, obscurely punctato- striated ; 

 strise diverging;, deepest upon the sides ; an- 

 terior slope straight, concave. 

 Syn. Plagiostoma Hoperi, Mantell Geol. of 



Sussex, 204, tah. 26,/. 2, 3,/. 15. 

 Nearly smooth between the longitudinal strije, which 

 are very commonly so obscure as not to be traced, except 

 close upon the sides, or near the edge : they are marked 

 with punctums in the same manner as P. punctata ; the 

 ears are unequal, not very prominent, they are striated. 



Sent me long ago by G. A. Mantell Esq. from Lewes ; 

 it occurs also at Northfleet, and other parts of theClialk 

 ranffe not rarely. . 



I fear that a single valve of this very distmct shell, 

 althou"-h similar in form, has been confounded with 

 Dianchora lata, tab. 80. and given rise to its being 

 described as plain, instead of striated, which the hgure 

 shews it to be ; the striae indeed are deep, but close and 

 regular, so that the surface has a smooth aspect. 



PLAGIOSTOMA rusticum. 

 TAB. CCCLXXXl. 



Spec. Char. Transversely oblong, oblique, 

 longitudinally sulcated ; valves convex ; 

 sulci deep; ears obscure; anterior slope 

 straight, convex along the middle. 

 A BOUT 25 deep irregularly disposed, and often curved 

 furrows, give the surface of this shell an unfinished 

 clumsy appearance ; the spaces between the furrows are 

 more or less flattened or convex, and are smooth ; they 

 are irregular in width, some specimens having them 

 widest in the middle, others at the sides of the valves ; 

 the ears, especially those upon the anterior slope, are 

 very short, and confounded with the eA^& of the shell; 

 the beaks are slightly prominent, the length is about two 

 thirds the width. 



Found in clay mixed with sand, consisting ot large 

 o-reen grains, upon Shotover Hill, near Oxford. 



