_Mya arenaria_, commonly known as the "soft" or "long-neck" clam, is found along the entire Massachusetts coast, wherever there is afforded a sufficient shelter from the open ocean. Exposed beaches with open surf are never inhabited by this mollusk, which is usually found on the tide flats of bays, inlets and rivers, and on the sheltered beaches between high and low tide lines. The clam occurs in various kinds of soil, from rocky gravel to soft mud, but grows best in a tenacious soil of mud and sand, where it lies buried at a depth of from 6 to 12 inches. As Cape Cod marks the dividing line between a northern and a southern fauna, it also divides the clam flats of Massachusetts into two distinct areas. The same clam is found both north and south of Cape Cod, but the natural conditions under which it lives are quite different. In comparing these two areas, several points of difference are noted. (1) The clam areas of the north coast are mostly large flats, while those of the south shore are confined to a narrow shore strip, as Buzzards Bay and the south side of Cape Cod for certain geological reasons do not possess flats, but merely beaches. (2) The rise and fall of the tide is much higher on the north shore, thus giving an extent of available flats nearly six times the clam area south of Cape Cod. (3) Clam growth as a rule is much faster on the north shore. This is due to the great amount of tide flow over the river flats of the north shore. Current is the main essential for rapid clam growth, as it transports the food. The average south shore flats possess merely the rise and fall of the tide, and as a rule have not the currents of the north shore rivers. (4) The temperature of the northern waters is several degrees colder than the waters south of Cape Cod. This affords, as has been shown experimentally, a longer season of growth for the southern clam. The north shore clam in the Essex region only increases the size of its shell through the six summer months, while the south shore clam grows slightly during the winter. The present advantages lie wholly with the north shore district, as through overdigging the less extensive areas of southern Massachusetts have become in most parts commercially barren. Overdigging has not occurred to the same extent on the north shore, owing to the vast extent of the flats. Nevertheless, many acres of these, as at Plymouth, Kingston, Duxbury, and even Gloucester and Essex, have become wholly or partially unproductive. The only important clamming in Massachusetts to-day is found in the towns bordering Ipswich Bay. The south shore and a good part of the north shore furnish but few clams for the market.