THE CYTHEREA. 353 



table. According to Mr, Maxwell, "a crowd of the more youthful description of the peas- 

 antry are collected every spring tide to gather Cockles on the sands by daylight when the tide 

 overruns. The quantities of these shell-fish thus procured would almost exceed belief ; and 

 I have frequently seen more than would load a donkey collected in one tide by the children of 

 a single cabin. They form a valuable and wholesome addition to the limited variety that the 

 Irish peasant boasts at his humble board ; and afford children, too young for other tasks, a 

 safe and useful employment.' 1 



This mollusk frequents sandy bays, and remains about low-water mark, burying 

 itself in the sand by means of the powerful foot, which also enables it to leap to a surpris- 

 ing height. 



The common Heart-Cockle and the remarkable Spiral Heart-Cockle differ in their 

 form, according to their name. The latter is notable for the boldly spiral umbones. 



The Spiral Heart-Cockle is in the habit of burrowing in the sand, leaving oidy the 

 openings of the siphon above the surface. In the Tuberculated Cockle these organs are at 

 once recognizable by their fringed edges ; and the large foot is seen below, carrying the super- 

 structure along. Even when taken out of the water, the Cockles are very lively ; and if 

 placed in a pan or basin they tumble about with great energy, knocking their shells against 

 each other and the sides of the vessel with remarkable activity. 



We now come to a group of these shells where the siphons are extremely long. The first 

 family is represented by the Banded Venus-shell, so called on account of its beautiful 

 colors and elegant form, and the bands which traverse its surface. All the Venus-shells are 

 handsome, and have well deserved their name. The shells are extremely hard in texture, 

 thick, and smooth, and are mostly found in the warmer seas. 



About one hundred and seventy species of Venus-shells are known, spread through- 

 out all parts of the world, and ranging from low-water mark to a depth of one hundred 

 and forty fathoms. 



The Venus mercenaria of America, or Quahog, is an important bivalve commercially, 

 ranking in this respect after the oyster and common clam {Mya arenaria). This shell-fish is, 

 fortunately for the inhabitants of our coast, who depend on some kind for food and profit, dis- 

 tributed where the mya is not found. This shell was a very important article among the 

 North American Indians. Beside depending greatly upon it as food, their money and orna- 

 ments were made from the shells. The blue of the interior of the shells was esteemed, and 

 bits of certain shape were used as media of trading transactions. 



The purple wampum was called by the New England Indians SucJcauhocJc. This was 

 valued at twice that made from the white shells. 



The beautiful Cytiierea is closely allied to the genus Venus, and is therefore appro- 

 priately named Cytherea, that being one of the classical epithets applied to Venus in conse- 

 quence of her predilection for the island of Cytherea in the iEgean Sea. In this animal the 

 two portions of the siphon do not diverge. 



In the family of the Mactridse, or Trough-shells, the valves are of equal dimensions, and 

 rather triangular in shape. The animal has the two channels of the siphon united as far as 

 the extremity, and the foot is ample and strong. 



The common Trough-shell is found on many coasts, always preferring those of a sandy 

 nature, where it can hide itself by sinking just below the surface. The foot is capable of con- 

 siderable motion, and can be extended to some length ; and when the movements are rapidly 

 performed, it enables the creature to jump about nearly as actively as the cockle. The 

 Trough-shells are found in all parts of the world, and in some coasts of the British islands are 

 so plentiful that they are gathered for the purpose of feeding pigs. The species which is 

 usually employed for this purpose is Mactra sitbtruncdta, and, like the cockle, it is taken 

 at low water. Although so usually inhabiting the zones just below and above low-water mark, 

 these shells are sometimes found as low as thirty fathoms beneath the surface. 



The largest bivalve on our shores is the Mactra solidissima, or Great Clam, so-called in 



Vol. in- 45. 



