Abstract: | The family Longosomatidae Hartman, 1944 (Annelida: Polychaeta) is newly reported for Icelandic waters. The diversity, taxonomy and ecology of this poorly-known monogeneric family are reviewed based on material collected during the BIOICE project. Two species of the genus Heterospio are recorded and redescribed: Heterospio longissima Ehlers, 1874 sensu Hartman (1965) and Heterospio reducta Laubier, Picard and Ramos, 1972–73. Several body structures of high taxonomic relevance in the genus are reviewed and discussed. |