Shell with the three nuclear whorls smooth and shining; the subsequent whorls have three revolving rows of nodules, of which the central row is most prominent; the last whorl has four rows of nodules, of which the two middle rows are stronger; suture deep; aperture small, subquadrate; canal deeply truncate, short; base below the last row of nodules smooth, concave. Color, pale brownish.
Length, 3; diameter, 0.75 mm.

Shell. Semitransparent and glossy. A rather tall cone which is markedly cyrtoconoid, most of the curvature towards the apex where the protoconch (usually lost) forms a narrow, almost styHform, top. The apical angle of shells of recently metamorphosed animals is c. 50°; this drops in shells with 3 whorls to 37.5±4.8° (range of 30-43°) and in full-grown ones to 17.7±2.2° (range 11-22°). There are up to 10 whorls in the adult shell, to which a further 4 belonging to the protoconch may be added. They are tumid and meet at deep sutures lying below the periphery of the upper whorl. The ornament consists of costae and of spiral ridges and grooves which together give a square reticulation accentuated by tubercles at its angles. The costae, ridges and intervening spaces are all about equal in breadth. It is the square depressed areas which are the noticeable feature of the ornament whereas it is the tubercles in the other species of Cerithiopsis. There are 4 spiral ridges on the last whorl, 3 on those of the spire. On the last whorl ridge 1 lies below the suture, 2 and 3 at the periphery, 4 below it; ridges 2 and 3 are often more prominent than the others. Ridge 4 is often not tubcrculate but smooth or, at most, slightly nodose. Some shells show a spiral ridge on the base encircling the columella; less frequently a second, thin spiral runs about half way between spiral 4 and the columella. In the spire there is no ridge on the adapical side of the suture. There are 20-22 costae on each whorl; they are commonly orthocline, but may be slightly prosocline or opisthocline. On the last whorl they form low ridges which may extend over the base as far as the columella but usually disappear before reaching it. There are fine growth lines in the square cancellation.
The protoconch has 4+ tumid whorls. They bear many small tubercles sometimes with an indication of a spiral lineation. In the older whorls those near the suture are bigger and in younger ones they link to form short prosocline costellae in the subsutural area. There is also a distinct spiral keel a little below the periphery. The final diameter is c. 200 µm.
Aperture. Oval, elongated along an axis lying at 30° to that of the spire. The outer lip (which is rarely unbroken) arises at the level of spiral ridge 4 on the body whorl, rather tangentially, and runs in a nearly semicircular course, continuing the outline of the spire, to the edge of the siphonal notch. There is no extension of this to form a canal. The columella is short, nearly straight and rolled like a scroll; the inner lip turns out and is applied to half its breadth. It also forms a thin glaze on the last whorl. The throat is glossy and shows the ornament and colour of the last whorl by transparency.
Colour. Yellow-brown. There are often 2 darker bands separated by an almost white one on the base, the upper below spiral 4, the lower at the base of the columella. The siphonal notch edge is dark and on the last whorl so are the spiral grooves. An occasional shell is white.
Size. Up to 6 x 1.5 mm. Last whorl = 40-50% of total shell height, depending on size of shell (50% in small ones, 40% in large); aperture similarly = 20-30% of height:
Animal. Unknown but presumably as in other Cerithiopsis spp.
Geographical distribution. A southern species extending north from the Mediterranean and Madeira to the Channel Islands, S.W. England and a few localities along the west coasts of Ireland and Scotland. It is rare.