(Pruvot, 1890)
Description:
Vermiform animals; in section the sides of the body are slightly concave so that the body is taller than it is wide. The dorsal surface bears a distinct keel formed by erect spicules while the ventral furrow is indistinct and tapers towards the rear of the body until it is visible only as a stripe leading to the sub-terminal cloaca. Cloacal gills or copulatory organs are absent. A dorsal sensory organ is usually distinct as a wart-like projection on the dorsal surface just anterior to the cloaca. The pharynx is protractable but there is no radula present.
The body surface is covered by scale-shaped spicules, which are up to 0.25 mm long and are found on the lateral surfaces; these spicules are truncated at their bases. Narrower spicules are mixed with the scale-like ones on the side of the body and in the region of the ventral furrow the scales are more lanceolate in shape (N. banyulensis-detail).
This species has been subdivided into two subspecies, N. banyulensis banyulensis and N. banyulensis norvegica . The latter form is distinguished by its smaller size (a maximum of about 15 mm long) and its more abruptly truncated spicule bases.
Size:
Up to 30 mm long, less than 1 mm broad.
Colour:
Greyish-red.
Habitat:
In depths of 45-300 m where they are epizoic on hydrozoans, principally Lafoea dumosa , Lytocarpia myriophyllum and Grammaria abietina , around whose branches they are coiled and upon which they are presumed to feed.
Distribution:
N. banyulensis banyulensis is a southern form found in the Mediterranean and along the Atlantic coast as far north as Plymouth. N. banyulensis norvegica is found in northern Europe (Distr. N. banyulensis).