No. 7. CARDIUM. 

 A Cockle. Inhabitant a Tetliys. 



Shell bivalve, nearly equilateral. Equivalves generally convex, longitudi- 

 nally ribbed, striated or sulcated, with the margin toothed. Hinge with two 

 alternate teeth in the middle, near the beak, in most incurved, lateral teeth 

 remote, and inserted or locking into the opposite. Forty-nine species of 

 this genus were described in the last edition of the Systema Naturae. 



The genus Cardium is somewhat cordiform in its shape, with the valves 

 denticulated or folded at the margin, beaks turned inward, hinge with 

 the two oblique teeth in each valve near the back, locking into each 

 other ; the ribs and furrows of the two valves are so disposed as to alternate 

 at the margin, and to lock accurately and firmly into each other. 



The word cardium is derived from xagSia, signifying heartlike, from the 

 cordate appearance of the genus. 



Upon the sandy shores of all the known seas, some of the species of Cockle 

 are to be observed. Most are found immersed in the sand, at the depth of 

 a few inches. Their size varies from five or six inches to half an inch in 

 diameter. The common Cockle is well known. All- the locomotive powers 

 of the Cockle are concentrated in the triangular yellow foot, which is so con- 

 spicuous when we open the shells. This foot is not only capable of great 

 inflexion, but also of seizing with its point the glutinous matter which pro- 

 ceeds from it, drawing this into threads, and thereby, in some measure, se- 

 curing the animals within the sand. Few shell fish are more common in inlets 

 and bays, and near the mouths of rivers, than these. In such situations they 

 are usually found, the place of each being marked by a small circular 

 depressed spot. When they open their shells, the entrance into these is 

 protected by a soft membrane, which entirely closes up the front, except in 

 two places, at each of which there is a small yellow and fringed tube, by 

 means of which it is that the animals receive and eject the water which con- 

 veys to their body the nutriment necessary for their support. Women and 

 children easily dig up this shell fish. Cockles in England and Wales are 

 sold by measure, and eat either raw, boiled, or pickled. They are deserv- 



