Source : Webster's Revised Unabridged Dictionary (1913)

Heteromyaria \Het`e*ro*my*a"ri*a\, n. pl. [NL., fr. Gr. ? other
   + ? a muscle.] (Zo["o]l.)
   A division of bivalve shells, including the marine mussels,
   in which the two adductor muscles are very unequal. See
   {Dreissena}, and Illust. under {Byssus}.