About Musculium lacustre (O.F.Müller, 1774)
The shell of Musculium lacustre measures 8 to 11 mm, and ranges in shape from oval to quadrangular. The umbos, which are capped by the juvenile shell, sit slightly forward of the shell's midpoint and face toward the anterior (front). The posterior (rear) end of the shell is broad and truncated. The shell itself is fragile, fairly glossy, and colored pearl grey to white. The outer periostracum (shell surface) has fine, even concentric striations. This species has a native Holarctic distribution, and is found on the following islands and in the following countries: Algeria, Belgium, the Czech Republic (occurring in both Bohemia and Moravia, and listed as near threatened, NT), Slovakia, Germany (listed as a species on the early warning red list), Great Britain, Ireland, and the Nordic countries of Denmark, Finland, and Sweden. It is not found in the Faroes or Iceland.
