Our eastern American oysters are undoubtedly the largest and finest for the table of the many species that exist all round the globe. Those of the Pacific coast of the United States are excellent, but small; and the same is true of the European species; nor is the use of oysters abroad so general and extensive as in the United States.
The pearl-bearing oysters are somewhat distant relatives of the edible oyster (Ostræa), the thorny oysters (Spondylus), the hammer shell, the windowglass shell (Placuna) and others. The pearl oyster of commerce is named Meleagrina margaritifera and is found in scattered localities within the tropics on both continents. The chief fisheries are in the Persian Gulf, around Ceylon, in Australia, among the Sulu Islands and on the west coast of Panama. The Pearl Islands, south of Panama, yielded to the early Spanish adventurers riches in gems that rivaled those their competitors obtained from gold mines; but now they are a field of small importance. In fact, the pearl fishery is carried on now far less in hope of a profitable collection of gems than for the profit in the shells, which have a nacreous interior of remarkable beauty—the mother-of-pearl—and the great advantage of offering this in almost flat surfaces, sometimes eight or nine inches broad, making it useful in the arts as well as in the more practical line of buttons, knife handles, etc. Sometimes the whole surface of a fine shell has been carved, cameowise, with cunning art and an exquisite effect.
[CHAPTER IX]
BUILDERS OF THE PEARLY SHELLS—Continued
MUSSELS, SCALLOPS AND CHITONS
The familiar marine mussels of the family Mytilidæ will some day become of great importance in this country as a food supply, as now they are useful in resisting encroachment by the sea on certain parts of the coast. They exist in vast numbers on both our coasts, and elsewhere in the world, in two genera, Mytilus and Modiolus, which differ a little in form, but not in habits. They have acquired the stationary habit, and in place of a "foot" of serviceable size have developed a gland that secretes an exceedingly tough, fibrous bunch of threads known as a "byssus," by means of which the animal may not only attach itself firmly to any sort of object, but may actually move about. The common species of Modiolus, the "horse mussel," lives in great numbers north of Cape Hatteras at and below the line of low water, and is much larger than the edible mussel just described. A smaller species of Modiolus is extremely numerous on the New England coast, and down to the Carolinas, forming dense tangled beds on muddy patches as well as among rocks, and serving to bind the mud and plants together and hold them from disintegration by stormy waves, in spite of the thin and brittle character of their shells. A southern species is bright yellow, with dark rays; and the common modiola of the Pacific coast is dark, glossy brown. Such mussels are eaten regularly in Europe, and come to us in a pickled condition as a luxury. There is no reason why we should neglect to add our own to our long list of sea foods.
The next useful mollusk to be considered is the scallop, one of the many species of the family Pectinidæ, of which we eat only the adductor muscle. The commercial species is Pecten irradians, the name referring to the (nineteen) ridges that radiate from the flattened hinges to the scalloped margin of the shell, which is prettily colored. This species is common in sandy, shallow places from Cape Cod to Florida, but the fishery is most productive about the eastern end of Long Island and in Narragansett Bay. Farther north is a very much larger species (P. islandicus) especially abundant on the Grand Banks, off Newfoundland, where it forms an important food of the cod and other fishes. It is well known to cooks, who use it in baking their fish confections en coquille. A large number of other species are distributed throughout the world, one (P. jacobæus), inhabiting the Mediterranean having the name "pilgrim shell" in allusion to the fact that in the days of medieval religious pilgrimages, those who had visited the shrine of Saint James at Santiago de Compostela, Spain, to pay homage on July 25, were accustomed to wear a scallop shell in their hats in token of the fact—this mollusk being connected with traditions of that saint.
Turning to the fresh-water mussels, or naids, as some books call them, one is staggered to learn that more than 1,500 species have been named, a large proportion of which belong to the United States, which is peculiarly hospitable to them because of our many rivers and lakes, together with the prevalence of limestone rocks, whose constant dissolution in water supplies the store of calcareous matter that these thick-shelled mollusks require. All belong to the family Unionidæ, in which two divisions are noted—one (Anodon) in which the mussel has a comparatively elongated thin shell with no "teeth" in the hinges; and the other (Unio) in which the shell is thick, various in shape from an oval to a triangle, and has prominent umbones, beneath which the valves (which are always alike) are hinged together by interlocking teeth embedded in a somewhat elastic gristle. The interior of all these unios is richly nacreous, and consequently pearls are produced in the same way as in the marine pearl-bearing shells; and some of the finest known gems have been derived from them, in this country and abroad, as well as innumerable specimens of moderate value. These mollusks like clear streams or lakes with a sandy bottom, and are not to be looked for in stagnant weedy waters. They keep an erect position, the nibs of the shell half buried in the sand, and move slowly about, plowing a path and dragging themselves along by means of the powerful foot, but keeping the short siphons at the other (or longer) end of the shell well above the mud.
We come next to our market clams. These are of two distinct kinds—"hard" and "soft," or quahog and long clam, as they are distinctively called. The quahog is a thick-shelled, roundish mollusk with a distinctly heart-shaped outline when looked at endwise. It dwells in fairly deep water, standing on its nibs half buried in the sand, like a wedge, and moving slowly about. Young ones become the "little necks" of our summer tables.