The shellfish are of two classes; the mollusks including clams, mussels (seldom used in this country), oysters, and scallops, and the crustaceans, - lobsters and crabs. None of the mollusks have high nutritive value, but they are a protein food, and add to the variety of the diet. The composition of the oyster is shown in Fig. 65, and it will be noted that the fat percentage is small and the calorie value low.

The oyster is raised in beds in the ocean, or bays often near the river mouth, and it is the neighborhood to the river that makes it possible for the oyster to carry germs of contagion, particularly of typhoid fever, when city sewage poured into the river passes over the oyster bed. Here, too, government protection is essential, and this is a matter that has created so much excitement that conditions are already improved. There is an association of oyster growers who make a point of advertising clean oyster beds, and cleanly methods of handling and transporting.

Oysters vary in size and flavor, the flavor seeming to depend upon the locality. The smaller are sought for serving raw, and the medium and larger for cooking. They are sold by the measure or number when taken from the shell, the latter giving the surer quantity; and the price is usually one cent apiece. They are in season from September to May. The whole flesh of the oyster is soft and edible, even the muscle by which it opens and shuts its shell being tender.

Clams are of two kinds, distinguished differently in different places. They are known as hard and soft, or round and long, and in Rhode Island the hard round clam still bears the Indian name Quahaug, the soft shell clam being the only "clam."

The long clam lies buried in the soft mud of creeks and muddy shores left exposed at low tide, when they are dug by hoes from the mud. The round clam lies on the bottom of shallow warm waters, and is raked with an implement made for the purpose. The round clam is used when very young and small in place of raw oysters; but both kinds when matured have a tough portion that is not softened in cooking, and that is more or less indigestible. The long "neck " which protrudes from the shell has to be discarded.

Both kinds may be roasted in the shell, and are very palatable served hot with melted butter, salt, and pepper. They are most commonly used in soups and in chowder. They are purchased by the quantity or number, are cheaper than oysters, and are always in season.

Scallops, as purchased, are only a part of the animal in the shell, consisting solely of the round white muscle which operates the shell. The escallop, or scallop, is migratory, moving by a shooting motion, the mature scallops reaching the creeks and shores in the autumn, and though found in so-called beds they are not fixtures like the oysters. The flavor is sweet, and they have a quality that makes them more or less indigestible, especially when fried. They are very palatable and more digestible served in a stew made like an oyster stew. They are sold by the measure and are cheap in season.

The lobster is now a luxury, for methods of catching in the past have made them scarce in their old haunts. The lobster is a much more highly developed animal than the mollusk, having strong muscles inside its coat of mail, and the flesh has a protein content that compares very favorably with meat. When fresh, and not served with rich sauces or eaten at irregular hours, it is not especially indigestible, and may be the main dish at luncheon or supper, served simply with salt, pepper, and melted butter and not taken with meat foods. Its own delicious flavor needs no addition in the way of sauces and high seasoning.

The crab is essentially like the lobster, being smaller, and having a sweeter flavor. The soft shell crab is caught just as the old shell is shed, and is highly esteemed as a delicacy. Both lobsters and crabs are cooked in the shell, and if allowed to die naturally before cooking they are uneatable. They may be purchased alive or cooked, and one is surer of their condition when they are bought alive. Twenty-five cents a pound is now an average price for lobsters in shell. Crabs are somewhat less expensive at times, but soft shells are always high-priced.

The following table shows the food value of a few of this group in terms of the weight of the 100-Calorie portion.