Morphological examination of several specimens of aeolid nudibranchs collected from the Ross Sea, Antarctica, revealed an unexpectedly high number of species. Based on the collected material the following species are re-described and for the first time their colour, reproductive anatomy and radula are illustrated together: Eubranchus glacialis, Cuthona modesta, Cuthona crinita, Cuthona elioti and Guyvalvoria paradoxa. Additionally, a new species of Cuthona is described from this area. The new species differs from other Antarctic and sub-Antarctic species of Cuthona in its external appearance, radular morphology and reproductive anatomy. Information on the egg mass and embryonic development of several species is provided.
