74 POPULAR BRITISH CONCHOLOGY. 



C. aculeatum : shell large, light, inflated, with about twenty 

 ribs adorned by prickles, the interstices of which are 

 smooth. 



C. echinatum : shell more solid, with fewer ribs, and the in- 

 terstices cross-ribbed. 



C. rusticum, generally called tuberculatum : shell thick, solid, 

 coloured by cross-bands of rich brown; ribs thick, 

 cross-ribbed, with little sharp tubercles. 



C. edule: the common cockle, so frequently used as food; 

 has a rather obliquely oblong shell with furrowed ribs, 

 and almost always with a patch of dark colour inside 

 at the hinder part, and about the hinge. The animal 

 inhabits sands at low water in numbers together. 

 Among the Orkney Islands, during the late failure of 

 the potato-crop, many of the poorer people subsisted 

 almost entirely on cockles. 



C. nodosum : shell small, rather square, with little oblong 

 seed-like tubercles on the close-set ribs. 



C. Suecicum : a delicate, small, white, flattish species. 



C.fasciatum: small, obliquely oval, banded with brown. 



C. pygmceum : like nodosum, but with little round tubercles 

 on the ribs. 



C. Norvegicum or IcRvigatum : rather large, flattish, smooth. 



