per·i·stome 
(pĕrĭ-stōm′)
(pĕrĭ-stōm′)n.
1. Botany A fringe of toothlike appendages surrounding the mouth of a moss capsule.
2. Zoology The area or parts around the mouth in certain invertebrates.
per′i·stomal (-stōməl), per′i·stomi·al (-stōmē-əl) adj.