SHELLS AND MOLLUSCOUS ANIMALS. 205 



The common cockle (Cardium edule) is one of 

 the most familiar objects on our shores, lying often 

 by hundreds, with the valves opened, because the 

 fish within has died ; or we may see the living 

 fish hastily scooping out a hole in the sand, just 

 below the surface, that it may bury itself, now that 

 our presence threatens danger. Nor is this the 

 only office performed by its strong fleshy foot, 

 bent, elbow-like., about the middle. When the 

 cockle wishes again to rise to light, it will double 

 up this foot, and, pushing it downwards against 

 the sand beneath, it can easily, by this process, 

 emerge from its hiding-place. By means of this 

 foot it can also leap so vigorously, that it has 

 been known to jump over the gunwale of a boat. 

 The number of the shells thrown on our sandy 

 shores, proves how numerous are these common 

 cockles in our own seas ; and the cockle tribe 

 abound also in the seas of temperate climates, as 

 well as in those of warmer regions. The fish is 

 eaten either raw or boiled in our land, and im- 

 mense numbers are sold for food in Holland during 

 winter, while it forms a truly valuable resource in 

 lands less provided with other means of food. The 

 shells of many of the species are also highly prized 

 by conchologists for their beauty. A small shell, 

 called the smooth-keeled-heart shell, is so valuable, 

 that Wood, in his work on conchology, states that 

 Dr. G-. Fordyce, who had one in his cabinet, 

 valued it so highly that he refused to take fifty 

 pounds for it. Several of the cockle species are 

 covered with spines, which probably serve to resist 

 the action of the waters, and hold their shells fast 

 in their sandy beds. Unlike the mussel, it has no 

 means of mooring itself, but all the species have 



