28 EOCENE MOLLUSCA. 



This fossil lias been hitherto assigned to 0. radiosa, Desh., and I feel reluctant to alter 

 the name ; but the large denticulations which are found invariably, in a greater or less 

 degree, on the inner margin of the upper valve in well-preserved specimens, appear to offer 

 a good specific character in contradistinction to the French shell of that name. 



15. Ostrea multicostata? Deshayes. Tab. VI, fig. 3, a, b. 



Ostrea multicostata. Desk. Coq. Foss. des Env. de Par., p. 363, pi. 57, fig. 3— 6. 



— — Bronn. Leth. Geogn., b. iii, p. 352, t. 36", fig. 6, a, c. 



— — ? D'Archiac. Anim. Foss. mimm. de l'lnde, p. 273, pi. 24, 1854. 



Spec. Char. 0. testa ovato-elongatd, subrectd, superne acuta ; valvd inferiore cosfatd, 

 cosiis divergentibus ; valvd superiore planulatd, lamellis tenuibus, concentricis, ornatd ; 

 impressione musculari obliqud. 



Shell ovately elongate, somewhat straight, with an acute umbo ; lower valve covered 

 with diverging ribs which bifurcate on the outer or older portion of the shell; upper 

 valve flat, with small or fine concentric lamina 1 or lines of growth j muscular impression 

 oblique. 



Height, 3 inches. 



Locality. Brackleshara {Edwards). 

 France, Retheuil {Desh.). 



A specimen in Mr. Edwards' collection corresponds with the figure and description by 

 M. Deshayes above referred to, and I have therefore regarded it as an identity, although it 

 is possible it may only be an enlarged growth of one of the Bracklesham varieties otflabcllula. 

 This is said to be abundant in France, where I presume there are better means of deter- 

 mining the species. The umbo in our shell is sharp and pointed, and the place of 

 attachment is very small. The upper valve is plain, or without the least appearance of 

 radiating striae. The muscle-mark is of a somewhat transversely ovate form, excentric, 

 and appears rather smaller, comparatively, than the one represented by M. Deshayes ; the 

 ribs in our shell are smoother or less scaly ; these trifling differences would probably 

 disappear in a large series. 



16. Ostrea picta, •/. Sowerby. Tab. VII, fig. ;2. 



Ostrea riCTA. J. Sow., in Dixon's Geoi. of £uss., pp. V5, 173, t. iv, fig. 1, 1850. 

 — — Morris. Catal. Brit. Foss., p. 175, 1851. 



Spec. Char. 0. testa crassd, orbiculari, intus purpurco-niyricanle, lamellis vix distinctly ,- 

 valvd inferiore profunda, valvd superiore planatd ; area cardinali lata ; impressione musculari 

 magna, suborbiculari. 



