Body narrow, tapering posteriorly.
Prostomium with a pair of short antennae without cirrophores, a pair of biarticulate palps of approximately the same length as the antennae and 2 pairs of eyes in a trapezoid arrangement.
Dorsal tentacular cirri longer than the ventral ones; second dorsal cirrus reaching chaetiger 8.
Pharynx with a pair of denticulate jaws; oral and maxillary rings with conical paragnaths (some have a wide base) absent from groups I and V; group II: 6-7; group III: 25-29; group IV: 17; group VI: 10-13; groups VII-VIII: a distinct row of large paragnaths with an irregular row of small paragnaths closer to the mouth.
Parapodia of the first two chaetigers uniramous with three lobes. Remaining parapodia all biramous with 4 lobes. Notopodial acicular lobe bilobed. In middle and posterior chaetigers lobes of the dorsal notopodial lobe, notopodial acicular lobe and the ventral neuropodial lobe are elongate. The neuropodial acicular lobe is as long as or slightly longer than the other three in anterior parapodia but much shorter in posterior parapodia; there is a well developed prechaetal lobe. Dorsal cirri as long as or shorter than the parapodial lobes, the ventral cirri shorter than the lobes (N. irrorata-parapodium). Notopodial chaetae are all homogomph spinigers. Neuropodial chaetae, homogomph spinigers and heterogomph falcigers above the acicula and heterogomph spinigers and falcigers below the acicula (N. irrorata-detail).
Up to 300 mm for 140 chaetigers.
Body yellowish or reddish to flesh-coloured, with white, grey or brown spots.
Dorsal cirri of the anterior unmodified region are thick in males and moderately thick in females and in the modified region smooth. In females modified parapodia begin on the 32-34 chaetigers.
Intertidal species, living in tubes.
North Sea, Sweden, north coast of France to the Mediterranean and North Pacific.