About Clausilia bidentata (Strøm, 1765)
Clausilia bidentata (Strøm, 1765) is a species of snail. Its shell is small, cylindrical, very high-spired and narrow, reaching 10–11 millimetres (0.39–0.43 in) in length. The shell is dark brown, with noticeable spiral ribs, slight longitudinal grooves, and a horny operculum.
This species occurs across much of western Europe; in the Czech Republic, it is found only in Bohemia, and it is also present in Great Britain and Ireland. It commonly lives under tree bark or within rock crevices. Individuals are most often encountered when they are active: at night during wet weather, when they climb trees to feed on lichens. Ecologically, this snail selectively grazes on lichens that grow on calcareous rock, particularly the crustose lichen Verrucaria nigrescens.
