Cyphoderia calceolus Penard, 1899
Diagnosis: shell pyriform, with a strong curved dorsal part, resembling a croissant or boomerang, usually colorless or faintly yellow, composed of numerous more or less small circular scales; scales not overlapping; shell in cross-section circular or faintly compressed; aperture circular or broad-elliptical; curved neck; fundus hemispherical or tapering to a more or less sharply-rounded apex; plasma with many dark granules; nucleus large, granular; fine straight filopodia.
Dimensions: Penard 155-185 µm; my measurements:
Ecology: debris of a small river in the Netherlands, some deep Swiss lakes.
Remarks: I have found this species in November 2011 in a sample from the Neerbeek-river in Neer, The Netherlands. In October 2012 I found this species in the river Weser near Bodenwerder, Germany.