Melinna cristata (Sars, 1851), a species commonly regarded as having a worldwide distribution, is re-defined following the examination of northern European material. As a result its junior synonym M. elisabethae McIntosh, 1885 is re-established as a valid species and a previously unrecognised species (M. albicincta sp.n.) described. In order to stabilise the nomenclature of the M. cristata-species group, a neotype is designated for M. cristata and a lectotype selected for M. elisabethae. A fourth species, M. islandica Saemundsson, 1918 is considered a nomen dubium, the original description possibly being based on an aberrant specimen of M. cristata. The affinities and geographical distributions of all three species are examined, and the taxonomy of the genus discussed.