ˈperəˌstōm noun
( -s )
Etymology: New Latin peristoma, from peri- + -stoma
1. : the fringe of teeth surrounding the orifice of a moss capsule
2. : the region around the mouth in various invertebrates: as
a. : the lip of a spiral shell
b. : the membranous area around an echinoderm's mouth
c. : the margin of the mouth opening of an insect formed by the skeleton of the head
d. : the area surrounding the mouth or cytostome of a protozoan