Gibbs, P.E. (1977). British sipunculans: keys and notes for the identification of the species. <i>Synopses of the British fauna (new series)</i>, 12. Academic Press: London, UK. ISBN 0-12-282050-9. 35 pp. (look up in IMIS) [details]
Littoral specimens are small, not exceeding 20 mm in length, while those from the sublittoral may attain lengths of 100-300 mm .