OSTREA, the oyster, in natural history, a genus of the Verrnes Testacea cLass'and order. Animal a tethys : shell bivalve, generally with unequal valves and slightly eared ; hinge without teeth, but furnish ed with an ovate, hollow, and mostly la teral transverse grooves. About 150 species have been enumerated, and class into sections and subsections. A. fur nished with ears and radiate ; scallop. B. rough, and generally plated on the out side ; oysters. C. hinge with a perpen dicular grooved line. Most of this genus are furnished at the hinge internally with numerous parallel transverse grooves in each valve, and are immediately distin guished from the genus area, in not hav ing teeth alternately locked in each other. Scallops leap out of the water to the dis tance of half a yard, and opening the shells, eject the water within them ; after which they sink under the water, and suddenly close the shells with a loud snap. 0. maxima : shell with about fourteen rounded and longitudinally striate rays ; is found in most European seas, in large beds, whence they are dredged up, and pickled and barrelled for sale. This, we are told, is the shell which was formerly worn by pilgrims on the hat or coat, as a mark that they had crossed the sea, for the purpose of paying their devotions at the Holy Land ; in commemoration of which it is still preserved in the arms of many families. 0. edulis : shell nearly orbicular and rugged, with undulate im bricate scales ; one valve flat and very en tire. Of this species there are many va rieties. They inhabit European and In dian seas, affixed to rocks, or in large beds ; the fish is well known as a palata ble and nutritious food. The shell is of various sizes, forms, and colours ; within white, and often glossy like mother of pearl ; the old shells have often an ano mia fixed to them, and are frequently co vered with serpulx, lepades, sertularia, and other marine productions. The fol lowing account has been given by Dr. Sprat of the treatment of oysters, in Great Britain.
In the month of May the oysters cast their spawn, (which the dredgers call their spats), it is like to a drop of a can dle, and about the bigness of a halfpenny. The spat cleaves to stones, old oyster shells, pieces of wood, and such like things, at the bottom of the sea, which they call cultch. It is probably conjec tured, that the spat in twenty-four hours begins to have a shell. In the month of
May, the dredgers (by the law of the Ad miralty Court) have liberty to catch all manner of oysters, of what size soever. When they have taken them, with a knife they gently raise the small brood from the cultch, and then they throw the cultch in again, to preserve the ground for the future, unless they be so newly spat that they cannot be safely severed from the cultch ; in that case they are permitted to take the stone, or shell, &c. that the spat is upon, one shell having many times twenty spats. After the month of May, it is a felony to carry away the cultch, and punishable to take any other oysters, un less it be those of that size (that is to say) about the bigness of a half-crown piece, or when, the two shells being shut, a fair shilling will rattle between them. The places where the oysters are chiefly catched, are called the Pont Burnham, Malden, and Colne Waters ; the latter taking its name from the river of Colne, which passeth by Collie Chester, gives the name to that town, and runs into a creek of the sea at a place called the Hythe, being the suburbs of the town. This brood and other oysters they carry to creeks of the sea, at Brickel Sea, Mer sey, Langno, Fingrego, Wivenho, Toles bury, and Saltcoase, and there throw them into the channel, which they call their beds or layers, where they grow and fat ten, and in two or three years the small est brood will be oysters of the size afore said.
Those oysters which they would have green, they put into pits about three feet deep, in the salt marshes, which are over flowed only at spring tides, to which they have sluices, and let in the salt water un til it is about a foot and a half deep. These pits, from some quality in the soil co-ope rating with the heat of the sun, will be come green, and communicate their co lour to the oysters that are put into them, in four or five days ; though they com monly let them continue there six weeks or two months, in which time they will be of a dark green. To prove that the sun operates in the greening, Tolesbury pits will green only in summer ; but that the earth bath the greater power, Brickel Sea pits green both winter and summer ; and for a further proof, a pit within a foot of a greening pit will not green ; and those that did green very well, will in time lose their quality.