Clausilia bidentata, the two-toothed door snail, is a species of door snails, terrestrial pulmonate gastropod mollusks in the genus Clausilia belonging to the family Clausiliidae, all of which have a clausilium.
This species is present in much of western Europe, including:
This species is commonly found under bark of trees or in crevices of rocks. The snails are often encountered when they are most active, at night during wet weather, at which time they often climb up trees and feed on lichens.
It selectively grazes on calcareous-rock lichens, particularly the crustose lichen species Verrucaria nigrescens.
The shell of this snail is a small and cylindrical snail, very high-spired and narrow. The shell length reaches . The shell is dark brown with noticeable spiral ribs, slight longitudinal grooves, and a horny operculum.