42 BIVALVES. — CARDIUM. 



Division III. — Sub-orbicular. 



llemies — Waved. *Zonata — Banded. 



*Fausta — Obsolete. Bimaculata — Double spot. 



*Reticulata — Reticulated. Balthica — Baltic. 



Cancellata — Cancellated. Pisiformis — Pea-shaped. 



*Guinaica — Gtdnea. Divaricata — Obliquely-striated. 



Scabra — Rough. Dentata — Toothed. 



*Crassa — Thick, Digitaria — Digital. 



Decussata — Decussated. *Cornea — Horn-coloured. 



Corcliformis — Heart-shaped. * Lacustris — Lake. 



Muricata — Prickly. *Aninica — River. 



Scobinata — Rasp. Pusilla — Minute. 



*Lactea — Milky. Limosa — Maton's. 



*Rotundata — Round. Fluminalis — Euphrates. 



*Flexuosa — Flexuous. Hermaphrodita — Olive. 



*Carnaria — Rosy. Fluminea — Ribbed. 

 Fluviatilis — Chinese. 



CARDIUM. — Cockle or Heart-shell. 



Animal — a Tethys : Shell bivalve, nearly equilateral, eqiii- 

 valve, generally convex, longitudinally ribbed, striated, or 

 grooved, with a toothed margin ; hinge with two teeth near 

 the beak, and a larger remote lateral one on each side, 

 each locking into the opposite. 



THIS genus, though not so numerous as the last, pre- 

 sents great variety of structure and colouring. There are 

 forty-seven species. 



The valves of the Cardium are for the most part of a con- 

 vex, swollen, or gibbous construction, and often spherical; 

 yet, in some instances, their form is elongated and com- 

 ]n*essed. In other species the contour exhibits the figure 

 of a perfect heart, as in the C. cardissa, &c. 



The shells are usually equivalve, and have their outsides 



