Per″i‐stome (pē̍r″ĭ‐stōm), n. [Pref. peri- + Gr. στόμα, -ατοσ, mouth.] 1. (Bot.) The fringe of teeth around the orifice of the capsule of mosses. It consists of 4, 8, 16, 32, or 64 teeth, and may be either single or double.
2. (Zoöl.) (a) The lip, or edge of the aperture, of a spiral shell. (b) The membrane surrounding the mouth of an invertebrate animal.