{{Short description|Body segment of an annelid worm containing the mouth and sometimes feeding palps}} The '''peristomium''' is the first true body segment in an [[annelid]] worm's body in the anterior end. It is directly behind the [[prostomium]] and contains the mouth, [[cirrus (Polychaeta)|tentacular cirri]], and sometimes feeding palps, which may instead occur on the [[prostomium]]. If an eversible [[Pharynx#Invertebrates|pharynx]] is present, it is contained in this segment as well, and can fill up to 20 segments when inverted, depending on the species.
The [[prostomium]] and peristomium can be variously fused, either completely distinct, or comprising a joint structure of a peristomial ring and a tentacular crown.<ref>{{cite book|last=Beesley|first=Pamela|title=Polychaetes & Allies: The Southern Synthesis. Fauna of Australia. Vol. 4A Polychaeta, Myzostomida, Pogonophora, Echiura, Sipuncula|year=2000|publisher=CSIRO Publishing|location=Melbourne, Australia|isbn=0-643-06571-7|pages=11–12|author2=Graham J. B. Ross |author3=Christopher J. Glasby }}</ref>
==See also== *[[Prostomium]] *[[Pygidium]]
==References== {{Reflist}}
[[Category:Annelid anatomy]]