Twee echte Balea’s in Nederland (Gastropoda, Pulmonata, Clausiliidae)

Next to the so-called well-known Balea (B.) perversa, there is another wide-spread consubgeneric species in western Europe, viz. B. (B.) heydeni. Here the latter species is reported from the coastal area of The Netherlands. It may be sympatric with B. (B.) perversa, which has been reported from all over the country. The conchological characteristics of the two species are described and illustrated, with possible differences in the colouration of the soft parts.