BIVALVIA. 75 



concent ricis, rcyidaribus, angmtis, elevalis (IG — 18) slriisque subtillissimis, coucentricis, 

 itnpressis. 



Shell small, suborbicular, much inflated ; umbones large, mesial, incurved ; posterior and 

 lower margins rounded ; lunulc very large, concave, its margins rounded ; the surfaces of 

 the valves have narrow, concentric, regular, elevated costae, IG — 18 in number, which are 

 impressed by very delicate concentric striations ; the intercostal spaces are upwards of three 

 or four times the breadth of the costa. 



Height, lateral diameter, and diameter through both the valves, each about 4 lines. 



About thrice the size of a minute Cotteswold Inferior Oolite species which possesses 

 a similar figure, but whose costae are irregular. Astarte Bulla, Goldf., is also globose, but 

 has only half the number of costae. A. integra, Goldf., has less convexity and is more 

 obHque ; other small species, figm-ed by Roemer, Buvignier, and by Quenstedt, have less 

 convexity and more obliquity. 



Geological Fosition and Locality. One of the more rare testacea of the Scarborough 

 Cornbrash; in the collection of Mr. Leckenby. 



Astarte Poxtonis, Lye. Tab. XL, fig. 31. 



Testa parva, convexa, ovato-orhiculari, umhonihus submedianis, acuminatis^ antrorsum 

 curvatis, maryine cardinali elonyato, subrecto, oblique declivi, lunula magna, costata ; valvis 

 costis concentricis numerosis (20) elevatis, rotundis, inierstiis angustis ; latere superiore, 

 area, elongata, planata et lavigata. 



Shell small, convex, ovately orbicular ; umbones elevated, pointed, nearly mesial, and 

 curved forwards ; hinge-border lengthened, nearly straight, sloping obliquely downwards, 

 forming a narrow, smooth area, separated from the costated part of the shell by an acute 

 angle ; the lunule is large, costated, and somewhat excavated ; the surfaces of the valves 

 have large, numerous (about 20) concentric, elevated, and rounded costae, separated 

 by more narrow interstitial spaces ; adult shells have a large fold of growth near to the 

 lower border. 



A small, convex, neatly ornamented species, allied to A. minima, Phil., and A. pisum, 

 Kock and Dunker ; from the former it is distinguished by the more numerous and more 

 closely arranged costae, by the more pointed and more curved umbones, by the larger 

 lunule, and by the posterior, straight, smooth, acutely bordered area; the latter feature will 

 also separate it from A. pisum and from A. supracorallina, D'Orb. 



The height and lateral diameter are about 4 lines. 



Geological Position and Localities. It is abundant in the White Oolite (Great 

 Oolite ?) of Ponton, Lincolnshire. 



