204 CARDIUM. 



ber and situation of the teeth of the hinge ; and although 

 it includes none but analogous species, yet the number, 

 owing to the researches of subsequent authors, and the 

 consequent advancement of the study, is augmented to 

 more than double the number described by Linnaeus. 

 There are, generally, four teeth in each valve, two of 

 which are situated close to the apex of the shell, and 

 are called by Linnaeus cardinal teeth ; the other two, 

 or lateral teeth, are remote, and all four lock into cor- 

 responding cavities in the opposite valve. Nearly all 

 the species of this genus are longitudinally ribbed. 



It must be observed, that we find in authors, the most 

 exact in other respects, a singular abuse of terms in 

 their designation of the ribs of cockles. Almost every 

 one, not excepting Linnaeus, has called them sulci, 

 which signifies grooves, and is in direct contradiction to 

 the fact, the ribs being a raised, not a depressed surface. 

 Baron Born was the first to rectify this error, who, re- 

 gardless of preceding authorities, was determined to 

 make the just distinction between ribs and furrows. It 

 will be proper to remark that, in the following specifica- 

 tions, in conformity with Baron Born's correction, we 

 have constantly substituted costa for sulcus, wherever 

 Linnaeus has used the latter word improperly. 



The animal inhabiting the Cockle, has two very short 

 tubes, which project from the anterior, and upper part 

 of the body ; the lower tube is the longest, and is pro- 

 vided with a pendent valve, by which it may be closed ; 

 both tubes are crowned with about thirty filaments, dis- 

 posed in two rows, of which those of the outer row are 

 conical, and stronger than the others. There is a fleshy 

 limb, shaped like an arm, with an elbow in the middle, 

 which proceeds from the body of the animal, and which 



