Clam

a popular name for certain bivalve mollusks. The word is akin to clamp, the two valves of the shell closing in a manner to suggest the jaws of a clamp or vise. The body is soft. The mouth parts are not developed. There is some popular confusion in the use of the term. Western people, in particular, apply the word to the mussel. Clams are found in salt water only. The most obvious difference between a clam and a mussel may be noted in the mantle. This has a thin, fleshy fringe which skirts the edge of the valves and enables the owner. at closing up time, to make a water-tight, even air-tight, joint. In case of the mussel this mantle runs clear around the edge of each valve and forms a continuous flap. The mantle of the clam is rounded out at one end of the shell into a notch, or "sinus," to permit the passage of a long "neck." When the mussel draws in and claps its valves together, nothing can be seen but shell ; when the clam shuts up, a round hole at the point of the shell is filled only by the end of the soft neck. The oyster has no foot at all. The mussel has a large foot. The clam is between and has a small foot. It is not much of a traveler. The young stay in the folds of the mother until they are pretty well developed. After they are ejected, they swim about on the surface of the water for a short time. As soon as the shell begins to form the young clam sinks to the bottom and attaches itself to a seaweed, or to a pebble, by a tough, gelatinous thread called a byssus. In case of the long-necked clam this thread disappears when the owner is about one-fifth of an inch long. This clam then burrows permanently in the mud and sand.

The clam of English coasts is called a piddock. It is collected for food and for bait. The young piddock settles on the surface of a clay bed, or soft rock, and scoops itself a hole by means of teeth on the shell. As the piddock grows, it continues to scoop; even at maturity the tip of the shell barely peeps above the surface of the ledge or clay. The piddock spends its life in this hole.

There are two well known clams on our Atlantic coast. One is found from Cape Cod to Texas. New Yorkers call it "a clam." New Englanders, by way of distinction, call it the "round clam" for the shape of the shell, the "hard clam," for its thick, rough shell and the "little neck clam," because the neck is smaller than that of the common New England species. The Indians call it the "quahog." This clam makes shallow burrows, but it may be seen also traveling slowly like a mussel, shell half in the water and half buried in the floor of the sea. A similar species is valued for food on the coasts of France. It is a warm water clam.

The second American clam is found from New York to Greenland. New Yorkers call it the "soft clam," the "long clam," and the "long-necked clam." Yankees call it "the clam," and think there is nothing like a clambake. The long-necked clam lives on tidal flats. With age, it sinks for protection into a permanent burrow or pocket, perhaps ten inches deep. This clam begins its burrow when young, deepens it as need arises, and stays in for a lifetime. Were he turned out in his old age he would have difficulty in making another. When the tide is in, a long "neck," containing both ends of a U-shaped tube, is thrust up to the opening of the burrow, a current of sea water is driven down one leg of the siphon, through the gills, and up the other leg of the siphon out to the sea. The gills of the clam get what air is required from this stream of water and, at the same time, strain out the minute animals and plants required for food. As is the case with all the clams, the current is propelled in part by the gills. When the tide goes out and the flat becomes bare, the clam draws down his long "neck," and closes his valves until the tide comes in again.

The New York fishermen collect clams by hand at low tide, or collect them from the bottom of the sea with a rake. The New Englander goes out on the flats at low tide and digs clams. Large and small, there are many species of clams. Nearly every coast has its clam. The so-called giant clam may be mentioned. It is a native of the seas of the East Indies. The two valves of the shell may weigh 250 pounds each. The natives of the Caroline Islands use fragments of the sharp-edged shell for axes. The body weighs some twenty pounds and is edible. Curiously enough, the scientific name of this clam, borrowed from the Greek, means three bites.

The clams of the Pacific coast are not considered equal to the "long neck" and the "little neck." Attempts have been made by the government to plant colonies of Atlantic clams on the Pacific coast.

See Mussel; Mollusk