The medusae of the subantarctic region are known through several papers, but there are some species that were not studied; these are new for science and for the region. Three new species and 1 new genus were studied: Euphysa monotentaculata sp. nov.; OCTOBULBACEA montehermosensis gen. et sp. nov. (Anthomedusae) and Solmissus atlantica sp. nov. (Narcomedusae). These species were caught with plankton nets of different types (biconic type with 200 microns gauze; bongo net with 350 microns gauze and Motoda net with 306 microns gauze). All these were compared with another species of the same genus, but most have their own anatomical features which are easily distinguishable from the others.Descriptors: EUPHYSA MONOTENTACULATA new species; OCTOBULBACEA MONTEHERMOSENSIS new genus new species; SOLMISSUS ATLANTICA new speciespls 1-2, map. (01.xii.1983).