common door snail

<em>Clausilia bidentata</em>, the common door snail, is a terrestrial gastropod mollusk in the family Clausiliidae. This species is distributed across Belgium, Denmark, Norway, and Sweden, where it typically inhabits moist terrestrial environments including deciduous woodlands, rocky slopes, hedgerows, and the margins of freshwater habitats. The common door snail is recognized by its elongated, sinistral (left-handed) shell, which is a distinctive trait of the family Clausiliidae. The shell is typically brown to gray and reaches approximately 12–15 millimeters in length. <em>Clausilia bidentata</em> generally feeds on algae, lichens, fungi, and decaying plant material by rasping food with a radula. It often shelters under bark, stones, and leaf litter during dry or cold conditions. Like many clausiliids, it possesses a complex internal shell structure called a clausilium that closes the shell aperture to reduce desiccation. The species is assessed as Least Concern, reflecting stable populations across its European range. Detailed biological traits beyond those noted here are not extensively documented in the current scientific literature.