Abstract
This study summarises the findings of benthic hydrozoans (Cnidaria, Hydrozoa, including Hydroidea and Siphonophora) collected around Iceland during the BIOICE programme. The vertical distribution of the encountered species is examined. Species diversity is highest in the upper 200 m and then decreases with increasing depth. Two new species were found: Eudendrium islandicum and Cladocarpus paraformosus. The following 15 species are new records for Iceland; Amphinema biscayana, Hydractinia borealis (polyp), Gymnogonos crassicaulis, Acaulis primarhis, Acryptolaria conferta, Campamilina panicula, Modeeria rotunda (polyp), Lovenella producta, Cladocarpus paraventricosus, Abietinaria pulchra, Abietinaria thuiarioides, Diphasia margareta, Sertularia similis, Kirchenpaueria bonnevieae, and Stephalia corona. The gonophores of Garveia biscayana Browne, 1907 and Stegopoma plicatile (M. Sars, 1863) are described for the first time. Both species produce free medusae. Garveia biscayana is transferred from the family Bougainviltidae to the Pandeidae as Amphinema biscayana comb. nov. Campanularia groenlandica Levinsen, 1893 is here recognised as a valid species and removed from synonymy with Campanularia volubilis.
