BIVALVIA. 135 



the valves rounded ; the surface smooth near to the apex, the remaining portion with large 

 concentric irregular striations. 



Locality. — 'This small species is not uncommon upon the slabs of Brandsby slate, and near 

 Scarborough ; it has not been identified in Gloucestershire. Mr. Williamson records it both 

 in the Great and Inferior Oolite of Yorkshire. 



Astarte elegans, Sow. Tab. XIV, fig. 14, vide antea, p. 86. 

 Ctprina ? dolabra, Phil., sp. Tab. XIII, fig. 19. 



Cytherea dolabra, Phil. Geol. York., 1, t. 9, f. 12. 



Testa par v a ovato-orbiculari, plano-convexa lavigata; umbofdbus subacutis mediants 

 elevatis ; marginibus rotundis ; lunula magna excavatd. 



Shell small, ovately orbicular, rather flattened, smooth ; umbones mesial, rather acute, 

 and elevated ; margins of the valves rounded ; lunule large and excavated. 



The depressed figure, elevated acute mesial umbones, and large lunule, separate it 

 from other small contemporaneous species of the Cyprinae. 



Height, 4 lines ; length, 5 lines ; diameter through both the valves, a line and a half. 



Locality. — Scarborough, in the Great Oolite. 



Isocardia cordata, Buck. Tab. XV, fig. 5. 



Isocardia cordata, Buckman. Geol. of Chelt., p. 98, t. 7, f. 1. 



Testa ovato orbiculari conveccd, umbonibus magnis obliquis antemedianis antrorsum 

 curvatis et separatis ; area ligamenti magna, sulco elongato, marginibus rotundis et integris ; 

 superficie lavi, striis concentricis tenuibus et irregularibus inslructis. 



Shell ovately orbicular or cordiform ; very convex near to the umbones, but rather 

 compressed at the margins, which are regularly rounded and entire; umbones large, 

 curved forwards, and separated by a large and lengthened ligamental area, upon each side 

 of which is a groove which extends nearly to the posterior extremity, and is bounded 

 above by an angle which may be traced to the extremities of the umbones ; the surface is 

 smooth, with fine irregular concentric striations ; test very delicate. 



Dimensions of the Yorkshire specimen ; height, 18 lines; length, 21 lines; diameter 

 through the valves, 15 lines. 



Localities. — Scarborough, in the Great Oolite ; larger examples, some of which have 

 the test preserved, occur in the Inferior Oolite of the Cotteswolds, but it is unknown in 

 the Great Oolite of Gloucestershire. 



QUENSTEDTIA LAEVIGATA. Tab. XIV, fig. ] 3. 



Psammobia laevigata, Phil. Geol. York., 1, t. 4, f. 5. 

 Testa ovato-elongatd, compressd, laevigata ; umbonibus depressis, medianis ; antice 



