352 THE COCKLE. 



The same ingenious people are also accustomed to make curious little pearl-covered josses, 

 by stamping them out in 1 1 1 in bell-metal, slipping them into the shell, and leaving them 

 between the valves until they are sufficiently coated with pearl. 



In the Thorny Clam, a curious member of another family, the shell is covered with long 

 and branching projections, something like the horns of a young roebuck. All the Clams are 

 natives of the warmer and tropical seas, especially among coral reel's, and their color and 

 shape are extremely variable. Mr. Broderip writes of them as follows: "The shells are 

 al tarlied by their external surface to submarine bodies, such as coral rocks, and shells have 

 been observed at depths varying from points near the surface to seventeen fathoms. These 

 shells appeal' to be subject to every change of shape, and often of color, that the accidents of 

 their position may bring upon them. Their shape is usually determined by the body to which 

 they are fixed ; and the development of the foliated lamina 1 which form their general charac- 

 teristic is effected by their situation ; and their color most probably by their food, and their' 

 greater or less exposure to light. The Chama that has lived in deep and placid waters will 

 generally be found with ils foliations in the highest state of luxuriance, while those of an 

 individual that has borne the buffeting of a comparatively shallow and turbulent sea will be 

 poor and stunted. 1 ' The Clams are generally attached by the upper valve. The animal is 

 edible, and is considered a great delicacy. About fifty species of Clams are known. 



The Tridacnidse are easily known by their deeply-waved shells, with the indented edges 

 fitting into each other, and the overlapping foliations of the surface. Although separated 

 from the true Clams, they are popularly called by the same name. The Yellow Clam is 

 often buried in a mass of white madrepores. A well-known species, called from its enormous 

 dimensions the Giant Clam (Tridacna gigas), was formerly rare, but is now tolerably plen- 

 tiful. It attains to a gigantic size, sometimes weighing more than live hundred pounds, and 

 containing an animal which weighs twenty pounds, and can furnish a good dinner to nearly as 

 many persons. 



The natives of the coasts on which it is found — namely, those of the Indian seas — are 

 extremely fond of this creature, and eat it without any cooking, just as we eat oysters. 

 The substance of the shell is extremely thick and solid, and enables it to be used for many 

 ornamental purposes. 



In former days, when this species was very rare, a magnificent specimen was presented to 

 the church of St. Sulpice, in Paris, where it may now lie seen, the valves being set up as 

 benitiers for containing the holy water. This shell dates from the time of Francis I. It is 

 evident, that the byssus by which so enormous a shell is moored to the rocks must be of great 

 size and strength, and, indeed, is so strong as to require an axe for its severance. The mus- 

 cles, too, by which the animal contracts its shell are enormously powerful ; and it has been 

 remarked by Mr. Darwin, that, if a man were to put his hand into one of these shells, he 

 would not be able to withdraw it as long as the animal lived. 



The Spotted Beak's-paw Clam has been placed in a separate genus, on account of a 

 difference in the number of projections on the hinge, technically called hinge-teeth. The 

 mouth is marked by a coronet-like circlet around it, and the foot is seen below just projecting 

 from its groove. 



This animal also spins a, byssus, which is, however, weak and slight compared with that 

 of the gigantic species just described. 



The family of the Cockles, or Cardiada?, so called from their heart-like shape, is well 

 represented by the common Cockle {Cardium edide). Generally, the Cockle is a marine ani- 

 mal ; but it sometimes prefers brackish water to the salt waves of the ocean, and a small 

 variety is found in the Thames nearly as high as Greenwich, when the water is sensibly 

 flavored with salt at each high tide. Another species, the Prickly Cockle {Cardium acu- 

 ledtum), is found on the southern coast, and regularly brought to market. 



The Cockle is gathered in great numbers for the purpose of being eaten, although, as the 

 greater number are consumed in the open air, they can hardly be said to be procured for the 



