14 
Venericardia. — Shell equivalve, inequilateral, suborbicular, mostly with longitudinal 
radiating ribs. Two oblique cardinal teeth, standing the same way. 
Plate XXI. Fig. 2- V. imbricata. — Fossil. [Mr. G. B. Sowerby’s Cabinet.] 
CARDIACEA. — 5 Genera. 
Cardinal teeth irregular, either in their form or in their situation; and in general accompanied by 
one or two lateral teeth. 
Cardium. — Shell equivalve, rather heart-shaped; the beaks prominent; the internal 
margins of the valves dentated or plaited : hinge with four teeth in each valve ; the 
two cardinal approximate and oblique, articulating cross-wise with the two in the 
other valve ; and two rather distant entering lateral teeth. 
(1) Shell with no particular angle on the beaks, and the anterior side at least as large as 
the posterior. 
Plate VIII. Fig. 1. (a) C. rusticum. (Idem. — Chem.) [Mrs. Mawe’s Cabinet.] 
( b ) Hinge of ditto. 
(2) Shell with the beaks carinated, or having an angle, and the posterior side often larger 
than the anterior. 
Plate VIII. Fig. 2. C. retusum. (Idem. — Linn.) 
Cardita. — Shell free, regular, equivalve, inequilateral : hinge with two unequal teeth, one 
short, straight, situated under the beaks ; the other oblique, marginal, and ex- 
tending under the corselets. 
(1) Shell subcordate, or oval, more transverse than longitudinal. 
Plate VIII. Fig. 3. (a) C. sulcata. (Chama antiquata.— Linn.) 
( b ) Hinge of ditto. 
(2) Shells more longitudinal than transverse. 
Plate VIII. Fig. 4. C. calyculata. (Chama calyculata. — Linn.) 
Cypricardia. — Shell free, equivalve, inequilateral, obliquely or transversely elongated. 
Three cardinal teeth under the beaks, and one lateral tooth extending under the 
corselet. 
Plate VIII. Fig. 5. (a) C. Guinaica. (Chama oblonga.— Linn.) 
(£>) Inside of ditto. 
Hiatella. — Shell equivalve, very inequilateral, transverse, gaping at the superior mar- 
gin: hinge with one small tooth in the right valve, and two oblique teeth, a little 
larger, in the left valve. Ligament external. 
Plate VIII. Fig. 6. (a) H. arctica. (Solen minutus; Mya arctica. — Linn-) 
( b ) Inside of ditto. 
Isocardia. — Shell equivalve, heart-shaped, ventricose, the beaks distant, diverging, spi- 
rally turned on one side : two flat, entering, cardinal teeth, one of them curved, 
