Salvini-Plawen, 1968
Description:
Shape characteristic, posterior body being tail-like slender and terminating in an orange-coloured tassel, sometimes coiled posteriorly; bodyform is unique for the species, enabling easy identification. Characteristic, clinging scales in the middle of body, whereas the scales of second region are similarly represented in other, non-Scandinavian species (F. crossotus-scales). Foot shield flanks mouth opening laterally, but does not close preorally (F. crossotus-detail). Digestive midgut gland is short, not entering the slendered posterior body. Ctenidia large and up to 11-12 alternating lamellae at each side.
Size:
Animals with ctenidia and typical shape measure from 3 to 25 mm, usually only up to 15-20 mm. Retractions or extension causes an alteration of up to 100 % in length (fully contracted 10 mm, fully extended 20 mm).
Colour:
Body brownish or even blackish veiled by distinct silver lustre. Slendered posterior body lighter, terminating in the orange-coloured pallial tassel. This orange-brown colour originates from secretion which also helps glue the spines. Ctenidia glimmer pinkishly.
Radula:
Two sickle-like radular teeth basally pointed and not showing a symphyse. Lateral supports simple, and like the basal plate, only strengthened distally.
Habitat:
Soft, muddy bottoms in depths of 30 to 470 m.
Distribution:
Skagerrak, the Norwegian Channel, Scandinavian fjords from Bohuslän to Lofoten. Until now there are no records from the Norwegian Sea and accordingly it is not known whether F. crossotus or a congener is native to these bottoms. One record from the west Scottish Firth of Lorne (Distr. F. crossotus).