60 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



wards; lunulc large, excavatedj hinge-border curved and sloping downwards; the extremities 

 are rounded and the base curves elliptically ; the concentric costse are regular, narrow, ele- 

 vated, the interstitial spaces having delicate longitudinal striations. The convexity is mo- 

 derate beneath the umbones, the extremities of the shell being rather compressed ; the 

 general figure approaches to C. Leymerii, Buy., but that species has the posterior side 

 shorter and less rounded. The present shell is more lengthened than is usual with the 

 Jurassic species, and the concentric costse are less conspicuous. 



Length, 19 lines; height, 12 lines; diameter through the valves, 9 lines. 



Geological Position and Locality. The upper portion of the Great Oolite, near 

 Minchinhampton, in pale, buff-coloured Oolite ; few specimens have been obtained, and 

 these, for the most part, are only casts. 



CoRBis ELLiPTiCA, Wldtcavcs, MSS. Tab. XXXV, fig. 1. 



Testa ovato-elongata, depressa, umbonibus parvis mediants, maryine antico subhorizon- 

 tali, postico oblique declivi ; basi elliptico curvato ; superjicie ruyis longitudinalibus regu- 

 laribus, magnis, elevatis, crebris. 



Shell ovately elongated, rather depressed ; umbones small, but little elevated, mesial ; 

 anterior margin nearly horizontal; posterior margin sloping obliquely downwards ; the two 

 extremities of the shell are rounded, and the base is curved elliptically ; the surface is orna- 

 mented with large, elevated, longitudinal, regular, and 'closely arranged rugae. 



Length, 7^ lines ; height, half the length. 



A small, depressed, and unusually lengthened Corbis, which will not readily be mis- 

 taken for any other known Jurassic species. 



Geological Position and Locality. The Forest Marble of Kidlington, Oxon., collected 

 by Mr. Whiteaves. 



CoRBis ROTUNDA, Walton, MSS. Tab. XL, fig. 17. 



Testa crassa, ovato rotundata, umbonibus magnis medianis antrorsum curvatis, lateribus 

 sub-aqualibus postice subcompressa, superjicie rugis concentricis magnis, crebris, sub- 

 (Equalibus ; (Btate adulto rugis obsoletis ; cardo dente antico laterali magno. 



Shell thick, ovately orbicular, subglobose ; umbones large, mesial, cm-ved forwards ; the 

 sides nearly equal, but the posterior side is slightly compressed and shortened ; the surface 

 with large, closely arranged, concentric, but somewhat unequal rugse, which degenerate in 

 the adult state and nearly disappear; 



It has sometimes been mistaken for Sphcera Madridi, but it is more orbicular, and the 



