Source : Webster's Revised Unabridged Dictionary (1913)

Epistoma \E*pis"to*ma\, Epistome \Ep"i*stome\, n. [NL. epistoma,
   fr. Gr. 'epi` upon + ?, ?, mouth.] (Zo["o]l.)
   (a) The region between the antenn[ae] and the mouth, in
       Crustacea.
   (b) A liplike organ that covers the mouth, in most Bryozoa.
       See Illust., under {Entoprocta}.