OSTREA. 



357 



1878. Ostkeum Leymeriei, E. Bayle. fixplicat. Carte geol. de France, vol. iv, 



Atlas, pt. 1, pi. cxxx, figs. 1, 2. 

 1897. Ostrea Leymeriei, R. B. Newton. Proc. Dorset Nat. Hist, and Antiq. 



Field Club, vol. xviii, p. 73, pi. i, 



fig. 3. 



Description. — Shell large, very thick in old specimens, higher than long ; 

 usually slightly or only moderately inequilateral ; outline ovate, oval, subtrigonal 

 or subquadrate. Left valve slightly or moderately convex; right valve often 

 flattened. Umbonal part sometimes narrow, sometimes broad. Umbo straight or 



^ 



Fig. 140. — Ostrea Leymcrii, Leym. Mammillatus-bed, Okeford Fitzpaine. British Museum, No. L. 11591. 



Interior of part of right valve, x f. 



slightly curved ; area large, high. Surface of valves sometimes smooth, except 

 for growth-laniellas, sometimes with radial folds. Attached surface of vari- 

 able size. 



Affinities. — This species seems to be related to 0. Germaini, Coquand. It also, 

 as de Loriol pointed out, shows some resemblance to some forms of Exogyra 

 sinuatam which the umbo is only slightly curved; but whether it has any real 

 relationship to that species cannot at present be determined. See also 0. cuna- 

 bula (below). 



Tijpe. — From the Barremian of Aube. 



47 



