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: 122-126 µm.

Ecology: Freshwater sediment: a small river in the Netherlands and the Weser river in Germany; Penard: some deep Swiss lakes.

Remarks: I have found this species in November 2011 in a sample from the Neerbeek-river in Neer, Netherlands. In October 2012 I found this species in the river Weser near Bodenwerder, Germany.