The nudibranchs collected by the Scottish National Antarctic Expedition comprise only six species, but these include two new and interesting genera.The species are—1. Notaeolidia gigas, gen. et spec. nov.2. N. purpurea, sp. nov.3. Tritonia appendiculata, sp. nov.4. T. pallida, Stimpson.5. Tritoniopsis brucei, gen. et sp. nov.6. Scyllaea pelagica, L.The Scyllaea was caught on the return voyage, in the Atlantic, 32° N., 33° W.; Tritonia pallida, off Dassen Island, forty miles north of Cape Town; Tritoniopsis brucei, off Gough Island, 40° 20′ S., 9° 56′ W.; and the three remaining species in Antarctic waters.