Source : Webster's Revised Unabridged Dictionary (1913)

Monomya \Mo*no"my*a\, Monomyaria \Mon`o*my*a"ri*a\, n.pl. [NL.,
   fr. Gr. ? single + ?, ?, muscle.] (Zo["o]l.)
   An order of lamellibranchs having but one muscle for closing
   the shell, as the oyster.