Oyster
2 of the 7 encyclopedias on this shelf carry an entry for Oyster. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a marine bivalve, or shellfish, much used for food. For a general description of the oyster, see article on the CLAM. An oyster may be distinguished from a clam, however, by the fact that the lower side on which the oyster lies is more rounding than the flat upper valve which acts more as a lid. As it does not travel the oyster has no foot like that of the clam and the snail. The oyster, like the mussel, lies in the water with its valves parted slightly. The hinge is near one end, and the water from which the oyster selects its food passes in, not by a siphon tube, but along the curved border and out at the straight border, being impelled by cilia, or waving, hair-like bodies. The young oysters are set afloat and swim a few days. A small shell then begins to develop, and the young oyster attaches itself to some object to which it becomes cemented for life by the bony material of the forming shell. Ordinary oysters are large enough to gather when four years old. Blue-points are ready at three. Oysters fresh from the water are fit to eat at any season, except from June to August. These months are the spawning season during which oyster fishermen desire to leave the oysters to breed. For these reasons it is just as well to heed the common saying that oysters are good only in months containing the letter R. There are about seventy species of oysters well distributed around the warmer seas. The common European oyster is gathered along the Atlantic from the coasts of Norway and the Baltic to a point as far south as the Mediterranean Sea . About 6,000,000 bushels of oysters are gathered annually in European waters. Half a million bushels of California oysters are gathered on the Pacific coast. The Virginian oyster is the most desirable species for food. When America was first colonized this oyster was found all along the coast from the St. Lawrence to the Gulf of Mexico. With the exception of beds in the Bay of Chaleur and on the coast of Prince Edward Island it has disappeared north of Cape Cod . Oyster fisheries still extend along the Atlantic coast from Cape Cod to Texas, with the center of the industry in Chesapeake Bay . Oysters are collected with a dredge, the bottom of which is shaped something like a comb. The oysters are torn loose by the teeth. They are caught in a bag which drags behind, and are brought to the surface. The annual oyster catch of the United States is from 20,000,000 to 28,000,000 bushels, worth about fifty cents a bushel at the wharf. The finest oysters are taken off the coast of Maryland and Virginia. Baltimore is the great oyster emporium of America,--the great oyster city of the world.
Collier's New Encyclopedia (1921)
a well-known edible shell fish, belonging to the genus ostrea, occurring in most parts of the world. The European oyster (O. edulis), which forms a considerable article of trade on the coasts of England and France, is taken by dredging, after which the animals are placed in pits formed for the purpose, furnished with sluices, through which, at spring tides, the water is suffered to flow. In these receptacles cles they acquire the green tinge so remarkable in the European oyster, and which is considered as adding to their value. The breeding time of oysters is in April or May, from which time to July or August, the oysters are said to be "sick," or "in the milk." This is known by the appearance of a milky substance in the gills. Oysters attain a size fit for the table in about a year and a half, and are in their prime at three years of age. From the observations and experiments of naturalists, it appears that they can move from place to place by suddenly closing their shells, and thus ejecting the water contained between them with sufficient force to throw themselves backward, or in a lateral direction. The lime obtained from the calcination of oyster shells, though exceedingly pure and white, is suited for work which does not require great tenacity, as for plastering rooms. The oysters most esteemed in the United States are the Virginian oyster (O. Virginiana) and the Northern oyster (O. borealis.) The flats in the vicinity of maritime cities are generally thickly beset with poles, indicating the localities of oyster beds. The principal sources of supply are the Chesapeake Bay, the coast of New Jersey, and Long Island Sound. Formerly the oyster beds were almost wholly kept up by restocking them with seed oysters from Chesapeake Bay and from the Hudson river; but of late years the spat is secured at spawning time, and new ground in the vicinity is brought under cultivation, till the area of oyster beds in Long Island Sound is now computed by miles rather than by acres, and it is yearly extending. Law as to Oysters. - The rule is that he who has the right of property in the soil or seashore is entitled to catch or keep a bed of oysters there. Whoever steals oysters or oyster-brood from an oyster-bed which is private property is guilty of felony; and whoever unlawfully or willfully uses any dredge, net, or instrument within the limits of a private oyster-bed, for the purpose of taking oysters, though none are actually taken, is guilty of a misdemeanor. In the United States there are various laws for the protection of the oyster industry, and applicable to various states, those relating to Virginia and New Jersey, being the most specific and strict.