Shell a rather tall, conical shell of 8-9 whorls, elongated basally into a short siphonal canal, solid, opaque, and glossy where periostracum is lost. The whorls are markedly tumid and meet at deep sutures which are a little incised. The apex of the spire is blunt and its sides (neglecting the curve of each whorl) usually straight, though a little coeloconoid in some shells. The apical angle is 35-40°. The ornament consists of spiral ridges and grooves, costae, and growth lines, which all cross to define a series of rectangular areas. The spiral ridges are V-shaped in section, a little broader than the intervening spaces and in the peripheral parts of the basal whorls tend to be alternately large and small. They extend to the tip of the siphonal canal. There are 23-27 on the last whorl, 7-9 on the penult, falling to 3 on the first postlarval whorl. The costae have the shape of a reversed C, are prosocline at the adapical suture, and become orthocline or slightly opisthocline as they cross the whorls; those on the last whorl die out at, or a little below, the periphery. They are undulate in section and rather variable in number, 12-17 on the last and penult whorls, then slowly decreasing up the spire, the first 2 postlarval whorls being ecostate. In a few shells, however, the number of costae on some upper whorls may be greater (20-22) than on the younger ones. There is no labial varix, and though the costae are crossed by the spiral ridges, there are no tubercles at the intersections. Growth lines fill the areas between costae and ridges. The periostracum is thickened along the latter and bears numerous hairs along them.
The protoconch has 1.5-1.75 whorls coiling round the same axis as the rest of the shell. The whorls lie in one plane, so producing the flattish lop to the spire. They measure 1.5-1.6 mm across. According to Marshall (1911) the protoconch is usually lost, though all the shells we saw possessed it. The first whorl is smooth, the second bears spiral ridges.
Aperture. An elongated oval surrounded by a peristome lying in a prosocline plane inclined c. 150° to the spire axis. The outer lip arises below the periphery of the last whorl, level with spiral ridge 11, at right angles to the shell axis. Its course to the siphonal canal is nearly semicircular and has a wide shallow anal sinus in its adapical half. The edge is thin and crenulated by the spiral ridges. The canal is short, widely open, bent to the left with its tip curved back from the apertural face of the shell. The columella is short and the inner lip spreads extensively over the last whorl, with a triangular area lacking pcriostracum alongside.
Colour. Shell white, covered with pale yellow periostracum.
Size. Up to 48 x 20 mm. Last whorl (including canal) 60-65% of total shell height; aperture = 40-45% of total height.
Animal. The head lacks a snout and ends in a shelf with the mouth underneath. From the shelf arise the tentacles which are not long and have, each, a laterally-placed eye, rather close to the base. The mantle edge is plain apart from the siphon on the left.
The foot is large, nearly straight anteriorly and pointed posteriorly. It bears an operculum which is oval in outline and has a terminal nucleus.
Colour. White or cream with dark markings on the siphon.
Geographical distribution. Not properly known, but these animals seem to occur the breadth of the Atlantic in high latitudes; on European coasts they extend as far south as the Straits of Gibraltar. They are not found in Danish waters and those collected off the British Isles come from off the west coasts of Scotland and Ireland.
Habitat. Soft bottoms in deep water to 1300 m.
Food, breeding and growth. Not known, though probably comparable with those of Co/us app., with food eggs and no free larval stage.