Webster's Revised Unabridged Dictionary · 1913

Epistoma

Epistoma , noun

[New Latin epistoma, from Greek 'epi` upon + {not transcribed}, {not transcribed}, mouth.]

(a)
(Zoology) The region between the antenna and the mouth, in Crustacea.
(b)
(Zoology) A liplike organ that covers the mouth, in most Bryozoa. See Illust., under Entoprocta.

Also: Epistome