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Rh the last traces of flesh, the radula may be soaked in a saturated solution of potassium hydroxide (KOH) for a few minutes. A solution of common lye will do as well. Animals whose flesh has been hardened by a preservative will have to be carefully boiled for a few minutes or soaked overnight in KOH or lye. Small specimens may be dropped whole into this alkaline solution if only the radula is desired. Transfer the radula successively to several watch-glasses of clean water in order to rid it of all traces of KOH. The radula may then be placed in one or two drops of water on a clean, glass microscope slide and, by observation under the dissecting microscope, a few teeth may be teased apart with fine needles. Leave some of the ribbon intact to show the relative position of the teeth. Add a square cover slip for study under the compound microscope. In water mounts such as these, stains are usually unnecessary. This temporary preparation may be permitted to dry for a day, the cover slip gently lifted, a few drops of euporol or mounting medium added, and the cover slip replaced to make a permanent slide. Some workers prefer to go from water to eosin stain to ninety-six percent alcohol and then to euporol, but this is an unnecessary elaboration. There are also excellent, permanent, plastic mounting mediums on the market. Canada balsam and glycerine jelly eventually deteriorate. Keep in mind that KOH or lye will burn flesh and eat holes in clothing.

Shape of shell. In most families of bivalves, the shape of the shell is extremely important as a species character, and only in a few groups, such as the oysters and mussels, is shape so variable within a species as to be of little taxonomic value. Shape of shell, as a whole, is of little value in determining families or genera, except in a few instances such as Pecten, Spondylus and Pinna.

Parts of the shell. The two valves of a clam are bound together by a brown, chitinous ligament, and usually hooked together by a hinge which is furnished with interlocking teeth. The valves are kept closed by powerful, internal adductor muscles but kept spread open by the action of the ligament when the animal relaxes or after it is dead. Each valve is a shallow, hollow cone, with the apex, from which point growth of the valves commences, turned to one side. This apex is termed the umbo (plural: umbos, umbones) or beak. The hinge and its teeth are usually just below the beak on the inside of the valve. The prodissoconch is the embryonic shell of the bivalve, and corresponds to the protoconch or nucleus of the gastropods. It is generally eroded away in adults, but when preserved it serves as a useful identification character, especially in such groups as the oysters.

Right and left valves. It is important to distinguish one valve from the