BIVALVIA. 145 



(Tab. XXII, fig. 2, from Brook), which appear to me to be a variety of this species. 

 These are not quite so much inflated ; they resemble much the figure and description 

 of C. Aizyensis, Desh., differing shghtly in the ornamentation. Our shells are not quite 

 orbicular, but have a greater diameter from the umbo to the ventral margin than in the 

 opposite direction. 



6. Cardita Davidsoni, Beshayes. Tab. XXII, fig. 17, a, b. 



Cabdita Davidsoni, Desh. An. sans Vert, du Bas. de Par., t. i, p. 7C4, pi. 60, figs. 



10—12, 1860. 



Spec. Cliar. C. Testa orbiculafo-suhtrir/onuld, depressiuscuJd, crassd, inaquilaterali, 

 radiatim costatd, costis 17 — 19 angustis, distantibus, obsolete tricarinaiis ; crenato- 

 squamosis, interstitiis latis, irregulariter striafis ; umbonibus aciitis ; lunuld minima, 

 Icevigald ; cardine crassiuscido. 



Shell roundedly trigonular, somewhat depressed, thick, inequilateral ; costated ribs 

 17 — 19, distant, narrow, and obsoletely triangular; outer keel covered with rather distant 

 squamose tubercles ; interstices broad, and covered with concentric striae or irregular lines 

 of growth ; beaks sharp, lunule small and smooth. 



Diameter, -fths of an inch. 



Locality. Barton. 



France : Ver. Ermonville {Desk.). 



This species is by no means rare hi England at the above locality ; it much resembles 

 C. sulcata, but it is not so tumid, the costae are fewer, more distant, the tubercles on the 

 ribs are not so numerous, the ribs are more angulated and not so rounded, and there is 

 generally a distinct line on each side of the keel. The elongated tooth is nearly parallel 

 with the ligamental fulcrum extending laterally beyond it. The valves are not so 

 frequently found united as are those of sulcata. 



7. Cardita deltoidea, /. Sowerby. Tab. XXII, fig. 7, a, b. 



Venertcaeuia deltoidea, J. Soiv. Min. Conch., tab. 259, fig. 1, 1821. 



— LATisuLCATA, Nyst. Coq. foss. de Belg., p. 209, pi. xv, fig. 5, a, b, 



1843, fide Vou K5nen. 



Spec. Char. C. Testa obliqud, subtrigond vel deltoidea, crassd, convewiusculd, incequi- 

 laterali, radiatim costatd, costis 15 — 18 acutis, elevatis, distantibus; lunuld magnd, 

 Icevigatd, depressd ; umbonibus elevatis, incurvis, obliquis ; cardine crassissimo. 



Shell oblique, subtrigoimlar or deltoidal, thick and strong, shghtly convex, inequi- 



20 



