59 



CHAPTER X. 



OF THE CARDIUM. GENUS VII. 



CARDIUM. 



" j\jiinial a Tethi/s. Shell bivalve, nearly equilateral and equivalved ; the 

 hinge with the middle teeth alternately in couples; the lateral teeth re- 

 mote and inserted." — Linn. 



1 HIS genus is very distinct from every other, the teeth scarcely 

 varying- in the different species. Tliere are two centre teeth 

 under the beak in each valve, standing in contrary positions ; 

 in one valve they stand side by side ; in the other valve they 

 are placed one before the other. They are all received into 

 hollows in the opposite valve, as may be observed in the com- 

 mon Cockle. There is always a lateral tooth on each side in 

 both valves, shutting into a hollow formed for its reception in 

 the opposite valve. They are in general strong thick shells, 

 very convex, and mostly with strong prominent ribs on the 

 outer surface, extending like rays from the beak to the margin. 

 The cartilage is short and external just under the beaks. 



The animal is commonly called a Cockle ; it is much like 

 the Tellina ; the mantle or palliutn is open in front ; it pro- 

 trudes two short tubes from the upper end of the shell, and a 

 scythe-shaped muscular foot from the front. 



Linnaeus has described 21 species, Gmelin has added 38, 

 and Dr. Turton 3. Total, 52. 



I 2 



