Poelslakken, andere raadsels en het ANM atlas-project

Questions raised by the recording of two Pondsnails: Radix balthica and R. labiata, from a tiny, artificial lake near Midsland, Terschelling, the Netherlands, are briefly answered. The name labiata has been used erroneously since the latter seems to be confined to Central Europe and the Alps (Bargues et al., 2001). Since the two types of Pondsnails living in that lake are readily distinguished on shell characters, while elsewhere in the Netherlands these two types seem to be infected by different types of parasites (Honer, 1960), they are considered as belonging to different species: Radix balthica and Radix species, till a better solution has been found. This complex of Pondsnails has not been dealt with in the Atlas-project of Molluscs in the Netherlands. Other, similar riddles dealing with land- and freshwater molluscs so far not included in the provisional maps are indicated.