CARUIACEA. 329 



lateral teeth, but sometimes none. Tliere arc four genera— 

 Cardium, Isocardia, Cardita, and Cijpricardia. 



The genus Cardium remains nearly as it was left by 

 Linngeus, and is very numerous in species. The common 

 Cockle, Cardium ediile, may be regarded as a type of the 

 series, their shells being more or less of a globular cor- 

 date form. 



Varieties of this interesting genus are met with on the 

 shores and in the depth of almost every ocean. He who 

 visits the muddy, flat, and desolate shores of Hudson^'s Bay, 

 may observe, for the space of at least ten miles, large num- 

 bers of the common species deposited upon the beach. They 

 tell him of other days, and other times, when the waters, 

 yielding somewhat of their ancient empire, receded from 

 the place they once occupied. The same species abounds 

 in Scotland, and is used in the Hebrides for skimming 

 milk. Macpherson hiforms ns, that, in the days of Fingal, 

 they were admitted into the feasts of heroes, as the cup of 

 their festivity, by the name of sliga-crechin, or the drinking- 

 shell. 



The genus Isocardia, though limited in species, is espe- 

 cially distinguished by the beautiful and novel structure of 

 the umboes, which, instead of terminating in immediate 



