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 ventral ones; second dorsal cirrus reaching chaetiger 2.
Pharynx with a pair of denticulate jaws; oral and maxillary rings with conical paragnaths, group I: 0-1; group II: 9-11 (7-13); group III: 13-17; group IV: 17-20 (16-25); group V: absent; group VI: 5-7 (3-9) in an irregular patch; groups VII-VIII: a distinct row of large paragnaths, with irregular rows of small paragnaths closer to the mouth (N. zonata-proboscis).
Parapodia of the first 2 chaetigers uniramous with 3 lobes.
Remaining parapodia all biramous with 4 lobes. Dorsal notopodial lobe smaller than the notopodial acicular lobe, and the ventral neuropodial lobe of similar shape to the notopodial lobes in anterior chaetigers, becoming slightly smaller and more bluntly to the posterior end. The neuropodial acicular lobe is shorter than the other three, with a poorly developed prechaetal lobe. Parapodia change little along the body. Dorsal cirri longer than parapodial lobes and ventral cirri slightly shorter (N. zonata-parapodium). Notopodial chaetae homogomph spinigers anteriorly, being replaced by 1 or 2 thick homogomph falcigers in more posterior chaetigers. Neuropodial chaetae homogomph spinigers and heterogomph falcigers above and heterogomph spinigers and falcigers below the acicula (N. zonata-chaetae).
Up to 125 mm for over 100 chaetigers.
Pink, yellowish, reddish or violet.
Body divided into 2 regions, an anterior region of 17 chaetigers in males and 16 in females, followed by chaetigers with modified parapodia. The dorsal cirri of the first 9 chaetigers in males are slightly modified, as are the ventral cirri of the first 7, whilst dorsal and ventral cirri appear to be unmodified in females. Metamorphosed parapodia from the posterior part of the body develop accessory flaps at the base of the dorsal cirrus, below the notopodial acicular lobe, on the posterior surface of the neuropodial acicular lobe and at the base of the ventral cirrus. The accessory flaps are more developed in males than in females. In males, crenulations develop along the lower edge of the dorsal cirri, and a pygidial rosette is found. In both sexes, the ordinary chaetae are replaced by paddle chaetae in the modified parapodia.
A subtidal species, living on hard substrata.
Widely distributed in the Arctic, in both the Atlantic and Pacific.