Body small and slender.
Prostomium as long as broad, bluntly conical, with a pair of eyes. Antennae short, indistinctly annulated; palps long with a short terminal section. Peristomium and apodous segment a little longer than following chaetigers.
Parapodium quite long, cylindrical, with equal chaetal lobes. Dorsal cirrus short, ovoid, present on all chaetigers. Ventral cirrus also ovoid. Supra-acicular chaetae of two kinds: (1) stout forked chaetae with subequal smooth branches; (2) 1-2 finely toothed capillary chaetae. Subacicular chaetae compound, with bifid, finely toothed stout hooked blades (P. kefersteini-detail).
A pair of short and a pair of longer annulated pygidial cirri.
Mandibles short, X-shaped, with finely toothed anterior margins. Maxillary carriers fused posteriorly, V-shaped. Maxillae: two upper rows and two lower rows of fine teeth; the basal plates of upper rows fused posteriorly, those of lower rows free (P. kefersteini-jaw plates).
Up to 15 mm for numerous segments.
Dorsal surface bright red or orange.
Mostly on sandy substrata, less commonly on mud; but also under stones, among sea grasses and algae, and in empty tubes of serpulid polychaetes. Occurs in the lower intertidal and the shallow subtidal zones.
North Atlantic to North Sea and English Channel, Mediterranean and Black Sea.