What is a division of bivalve shells, including the marine mussels, in which the two adductor muscles are very unequal. See Dreissena, and Illust. under Byssus called?

heteromyaria — A division of bivalve shells, including the marine mussels, in which the two adductor muscles are very unequal. See Dreissena, and Illust. under Byssus. (Webster's 1913.)

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