60 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



wards; lunule large, excavated; hinge-border curved and sloping downwards; the extremities 

 are rounded and the base curves elliptically ; the concentric costas 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. Ley-merit, Buv., 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 

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

 these, for the most part, are only casts. 



CORBIS ELLIPTICA, Whiteavcs, MSS. Tab. XXXV, fig. 1. 



Testa ovato-elonffata, depressa, umbonibus parvis medianis, margine antico subhorizon- 

 tali, postico oblique declivi ; basi elliptico curvato ; superf.de rugis 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 5 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 antrorsinn curvatis, laieribus 

 sub-cequalibus postice subcomjtressa, superficie rugis concentricis magnis, crebris, sub- 

 cequalibi<s ; atate adulto rugis obsoletis ; cardo denle antico laterali magno. 



Shell thick, ovately orbicular, subglobose ; umbones large, mesial, curved forwards ; the 

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

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

 the adult state and nearly disappear. 



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



