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 CHAPTER III

the approximate 15,000 species of existing clams or bivalves, four fifths live in the sea, while the remainder are inhabitants of fresh-water rivers, lakes and ponds. Throughout the seventy or so familes of this class, the clams show an amazing diversity of ways of adapting themselves to almost every kind of aquatic environment. There are clams that swim, burrow, dangle by silken threads, others that are permanently cemented to rocks and corals, some that live a sedentary life of attachment to other marine creatures. In size, they vary from the 500-pound giant Tridacna clams of the East Indies, which reach a length of over four feet, to the pinhead-sized Amethyst Gem Shells (Gemma), which so heavily populate some of our intertidal flats. In ornamentation and coloration the clams are almost unexcelled in their wide range of beautiful hues and bizarre shapes.

WHERE THEY LIVE The bivalves have selected a wide variety of ecological stations in life. While many must live in strictly marine waters, a few have adapted themselves to the brackish waters and estuaries and inland bays. One species, the ’Coon Oyster of Florida and the West Indies, has “taken to the trees” and is able to withstand exposure to the air for several hours, or even days, between high tides. In its early, free-swimming stages, the oyster is carried by the rising tide in among the roots, trunks and overhanging boughs of the mangrove trees where it settles and attaches itself. Feeding, growth and reproductive activities take place only during the few short hours of high