524 



MOLL use A. 



haviiij,' boaril of llowcll's gooil aii.l l-inl lortiim-, became a pearl-hunter, and, after wading about 

 in tho nmd of Notoh lirook for many days, found a mussel from which he extractcl a splendid 

 pearl, live-ei:jliths of an inch in diameter. It was of })erfect form and pure colors, and was sold 

 to Messrs. 'ntTany S: C\... of New Yt>rk, for a thousand dollars. This was sent to Paris, and re- 

 sol.l for twenty-two hun.lred dollars. Those incidents produced a general pearl-hunt all over the 

 country, and a number of small pearls were found; but the search was, on the whole, unsuccess- 

 ful, and it is now abandoned. 



THE MYTILACEA. 



Tliis iiichules several genera of what are properly called Mussels ; these live mostly, if not 



entirely, in salt water; the fish has a byssus by 

 which the animal usually attaches itself to some rock 

 on the shore. The valves are generally equal, of an 

 elongated form, and pearly inside. Many of the 

 species conceal themselves by burrowing into various 

 substances ; some can penetrate rocks, corals, and 

 shells for this purpose. Some species make use of 

 the byssus to spin themselves a sort of net. Though 

 inferior to the oyster, immense quantities of the 

 Common Mussel, Mytilus edulis, arc eaten in Eu- 

 rope : four hundred thousand are said to be annually 

 consumed in Edinburgh and Leith, and thirty or 

 f(M'ty millions to be used for bait in the Frith of 

 Forth. Several species of this genus occur on our 

 American coasts. 



THE COMMON MUSSEL. 



THE AKCACEA. 



In these the shells are nearly equal, usually thick and furnished with a long row of teeth at the 



hinge. Among them is the Area tortuosa, 

 the shell somewhat twisted and striated ; 

 found in the Indian Ocean. The A. j^exata, 

 W-^M^^^WSi'-\ common on our coasts, is called the Bloody 

 Clam, because, on being opened, there issues 

 from it a flow of reddish liquid. There are 

 other American species. The A. transversa 

 is common from Cape Cod to the coasts of 

 New Jersey. 



THE AHCA TORTUOSA. 



THE AVICULACEA. 



In this tribe, which is rendered important by its including the Pearl-Oyster, the foot is 

 small, and produces a byssus by which the aninuil attaches itself firmly to submarine objects. 

 The mantle lobes are free ; the shell usually oblique and somewhat triangular, with the valves 

 unequal, and the hinges without teeth. 



Most of the shells are pearly in the interior ; and as the true pearls are merely morbid growths, 

 they may all produce pearls of various qualities. The formation of pearls is caused by the intro- 

 duction of irritating substances, such as grains of sand, between the mantle and the shell. The 

 irritation causes the animal to cover the obnoxious object with layers of pearl, which generally 

 attach the foreign body to the interior of the shell. The Chinese produce pearls artificially by 

 placing substances in the position thus described. 



The Pearl-Oyster, Mcleayrina margaritifera, furnishes the finest pearls ; the shells are also 

 imported in vast quantities, the inner layer, known as " mother of pearl," being used for a great 

 number of ornamental purposes. This species is found in various parts of the Indian and Pacific 

 Oceans, at a depth of about twelve fathoms, where they are taken by divers. A considerable 

 number of pearls are procured on the coasts of Panama, but many of them are of irregular form. 



