(Linné, 1758)
Description (shell):
Shell with slender, elongate spire. Whorls almost straight-sided with deep, flat sutures; marked with thick, flat, slightly sinuous, oblique costae, indistinct on first whorl, prominent thereafter; abapical portion of body whorl smooth with few very faint growth lines; no concentric grooves between costae. Protoconch smooth and rather bulbous. Aperture rather square, thickened in older shells; no umbilicus. Deep orange operculum (T. lactea-drawing).
Size:
Up to 9 mm with ten whorls and protoconch.
Habitat:
Lower shore and subtidally, feeding on sedentary worms, such as Audouinia and Amphitrite .
Distribution:
At various localities in the North Sea (Distr. T. lactea).