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Anatomical feature of annelids
This article is about a bristle-worm anatomical feature. For the snail of Aciculidae family, see Acicula (gastropod).
Hutchings, P. A.; Fauchald, K. (2000). Polychaetes and Allies: the Southern Synthesis - Class Polychaeata: Definition and General Description. Melbourne: CSIRO Publishing. pp. 1–3.