The shell is of moderate size for the Trophoninae (maximum length 16 mm) and typically fusiform. The spire is high, consisting of one and one-half smooth, convex nuclear whorls and six convex to weakly subangulate postnuclear whorls. The suture is moderately impressed. The body whorl is of moderate size, long, and fusoid. The aperture is moderately small and ovate, with a narrow, shallow anal sulcus. The outer apertural lip is very finely serrate marginally, reflecting the spiral shell sculpture, briefly, finely lirate within, and strongly indented at the origin of the siphonal canal. The columellar lip is smooth and entirely adherent. The siphonal canal is long, open, and bent to the left.
The body whorl bears nine to 12 low axial ridges, some of which may represent varices. Spiral sculpture consists of up to 16 cords, 12 on (he bodv and four on the canal, all essentially of the same size; where these cords intersect the axial ridges they are slightly uplifted, imparting a scabrous texture to the shell. Shell color is orange-brown, red-brown, or purple-brown, covered in uneroded specimens by a thin, white intritacalx and a fuzzy, yellow or orange-brown periostracum.

Shell. Fusiform, solid, opaque and slightly glossy when, as is usual, there is no periostracum present; sometimes this persists and then may be a little hispid. The spire is tall, rather narrow (apical angle 36-42°, commonly 37-38°), and straight-sided. The 7-8 whorls are markedly swollen and meet at deep sutures lying below the periphery of the upper whorl; they are angulated, flattened at the periphery, and like a half hexagon in profile. The ornament comprises costae growth lines, and spiral ridges and grooves which all interact to cover the surface with a criss-cross pattern, elevated at the nodes to form small tubercles. The costae arc slightly prosocline, distinctly so where they abut the adapical suture, and are about as broad as the intervening spaces; they are often steeper on the leading edge, cross the whorls of the spire, but on the last whorl fade below the basal end of the peripheral flattening. There are 15-17 on the last whorl, 15-20 on the penult and a steadily decreasing number on those higher in the spire. Spiral ridges are absent from a flat area near the adapical suture of each whorl; 3 or 4 ridges (equal to the intervening spaces) occupy the area between that and the periphery, below which they become crowded and broader than the grooves. They fade on the siphonal canal. There are 11-15 ridges on the last whorl. 5-6 on the penult, the number reducing up the spire to 2-3 on the most apical below the protoconch. Spiral ridges and costae together give a square cancellation, oblong near the periphery, especially on the last whorl.
The protoconch has 1.5 whorls, smooth and glossy but with many fine growth lines and some spiral markings in its earlier parts, 850-1000 µm across. There is an abrupt boundary between it and the adult shell on which it lies a little obliquely.
Aperture. A pyriform opening, broader adapically, surrounded by a peristome lying in a very slightly prosocline plane and exhibiting an extremely shallow anal sinus. The outer lip arises level with the 5th or 6th spiral ridge at right angles to the last whorl and so at 110° to the axis of the spire. It then curves to the base of the siphonal canal into which it turns smoothly but rather sharply. Its edge is thin and sinuous because of the ends of the spiral ridges and grooves. The siphonal canal is rather long (= about a quarter of the total shell height), nearly straight, in line with the long axis of the aperture but with the distal half bent away from the apertural side of the shell. It is about half open along the outer lip side. The columella is nearly straight and extends to cover half the siphonal canal. The inner lip is everted at columellar level and over the last whorl to which it is so closely applied that its edge is hardly visible. The throat is marked by ridges and grooves within the outer lip reflecting the external ornament; the inner lip and throat are glossy and smooth, though marked with innumerable microscopic papillae. ,
Colour. Yellowish, with darker brown bands below the sutures and at the base of the last whorl, the periphery of which is paler. The siphonal canal is yellow, the peristome and ribs pale. The bands arc little visible in some shells, and a few are quite colourless.
Size. Up to 19 x 8 mm. Last whorl (including siphonal canal) = 68-78% of total shell height; aperture (including canal) = 50-60% of total shell height.
Animal. There is hardly any head, the cephalic tentacles arising from a low bulge on the anterior face of the neck between foot and visceral hump. They diverge markedly and arc not linked by any transverse fold. The mouth (= opening of a proboscis pouch) is a small slit under the insertion of the tentacles. An eye sits on the lateral surface of each tentacle, rather more than halfway from base to top; distal to the eye the tentacle is slender and pointed. The mantle edge is smooth, extended on the left into a siphon which projects little from the siphonal canal. Males have a penis, kept recurved in the mantle cavity, arising from the floor behind the right tentacle.
The foot is rather long, especially in its anterior part, the front of which has a rounded, double edge, a little pointed at its corners, and ends bluntly behind.
Colour. Cream, white.
Geographical distribution. This species occurs from the Mediterranean northwards to the south and west coasts of the British Isles. It is probably not Scandinavian, though mentioned as occurring off southern Norway and western Sweden by Ankel (1936).
Habitat. On muddy, sandy and gravelly bottoms from about 20-300 m.
Food. Unknown, perhaps small annelids.
Breeding and growth. Breeding was recorded by Lcbour (1936. 1937) at Plymouth between February and June. The eggs (480 um across) are laid in lens-shaped capsules (also described by Fioroni, 1966) which are circular in outline and fastened by the flat surface to a substratum. A capsule may be 1.8-3.1 mm in diameter and 0.75 mm high, is transparent, with an apical hole plugged by mucus through which juveniles escape. The wall of the capsule is thick and its outer surface wrinkled. The veliger stage is intracapsular and the animals seem to hatch with a shell of 1.5 whorls, 640 µm across, its initial part punctate, and already with a siphonal canal. The body of the animal is nearly colourless.

Several authors (Franchini & Frilli, 1970; Houart, 1981) have recently synonymized T. barvicensis and T. muricatus. As we have discussed under T. barvicensis we do not find the evidence for this convincing enough. We have seen samples with the two forms occurring sympatrically, from the Bay of Biscay and N Morocco, from 120-200m. We have, however, also seen samples where it seems impossible to distinguish the two (e.g. from the Adriatic, coll. G. Spada. Bologna). The Mediterranean material we have seen has been insufficient to ascertain whether barvicensis really occurs in the Mediterranean and the problems are caused by a higher variability of muricatus there, or if they really integrade. The latter seems to be supported by Chaster's (1898) observation that they intergrade in the British Isles, but contradicted by our observations from other areas. Therefore we prefer to leave the question open and treat them as two species.

European coastal areas, from Great Britain south to the Mediterranean and Morocco, in 20 — 300 m.