Cornelius, P. F. S. (1995). North-West European Thecate Hydroids and their Medusae. Part 1. Laodiceidae to Haleciidae. <em>In: R.S.K. Barnes & J.H. Crothers, eds, Synopses of the British Fauna (New Series). The Linn. Soc. London and Est. Coas. Sci. Ass. - Field Studies Council.</em> 50 : i-vii, 1-347. (look up in IMIS) [details]
Medusa: Diameter up to ca 22 mm, often less in British waters.