Within the genus
Prionospio Malmgren, 1867, the ‘
steenstrupi-group’ (including the type species
P. steenstrupi Malmgren, 1867) is characterised by the possession of four pairs of branchiae, of which the first and fourth pairs are pinnate. Unfortunately the identities of
P. steenstrupi and the other northeastern Atlantic species (
P. fallax Söderström, 1920 and
P. dubia Maciolek, 1985
[sic, actually Day 1961]) have been much confused. All have been variously misinterpreted or synonymised in the literature. An examination of type, topotypic and other European material indicates that all three species are valid and readily distinguished. Each species is described and figured in detail, and their geographical distributions reassessed. The usefulness of the characters employed to distinguish these and other species is discussed. It is recommended that assessments of intraspecific variability be included in all species descriptions.
