(Johnston, 1825)
Description (shell):
Shell similar to that of Trophon truncatus in having predominantly axial ornament in the form of well-spaced, narrow costae which show a marked elevation at the lower edge of the subsutural ramp. Spiral ridges also occur making the costae tuberculated or wavy where they cross them. Spiralridges are absent from the subsutural area. There are 11-13 costae on thelast whorl, 12-14 on the penult; the corresponding numbers of spiral ridgesare 6-8 and 3-5. Siphonal canal long and delicate. There are about seven tumid, semi-transparent whorls with deep sutures.
The outer lip is thin and (if a costa lies along it) shows an out-turned hollow spine at the point where the costa is elevated. Last whorl occupies 70-75 % of shell height, aperture 60 %.
Size:
Up to 15 x 7 mm.
Colour:
White or colourless, occasionally with some yellow along the costae.
Animal:
Distal third of cephalic tentacles narrow, with eyes set on lateral bulges at junction with broader basal portion. Foot with double-edged anterior margin and slight anterio-lateral horns; operculum small, oval.
Habitat:
The animals are not uncommon in dredgings from stony bottoms.
Distribution:
From Iceland and north Norway, where they live at a depth of a few metres, to northern and western localities in the British Isles, where they are more likely to occur 40-140 m deep. They live still further south at increasing depths. Not in the southern North Sea (Distr. T. barvicensis).