42 BIVALVES. CARDIUM. 



DIVISION III. Sub- orbicular. 



Remies Waved. *Zonata Banded. 



*Fausta Obsolete. Bimaculata Double spot. 



*Reticulata Reticulated. Balthica Baltic. 



Cancellata Cancellated. Pisiformis Pea-shaped. 



*Guinaica Guinea. Divaricata Obliquely-striated. 



Scabra Rough. Dentata Toothed. 



* Crassa Thick. Digi taria Digital. 

 Decussata Decussated. *Cornea Horn-coloured. 

 Cordiformis Heart-shaped. * Lacustris Lake. 

 Muricata Prickly. *Amnica 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, eqid- 

 valve, generally convex, longitudinally ribbed, striated, or 

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

 the beak, and a larger remote lateral om 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 j 

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

 pressed. 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 



