Cyclopyxis plana var. microstoma Schönborn, 1966

Diagnosis: Shell small, flat and yellow-brown in color, covered with single flat mineral grains. Aperture ventrally, circular and occupying at most 1/3 of the shell diameter.

Dimensions: According to Schönborn (1966): Shell diameter about 45 μm; height about 20 μm.

Ecology: Freshwater. Pond.

Geographical distribution: Spitsbergen.

Remarks: The form resembles strikingly the kind described by Bartos from Java, Indonesia, as Cyclopyxis plana Bartos, 1963. It differs from it by the somewhat deeper intussusception of the aperture (5 µm) and by the much smaller aperture. However, as with the form described by Bartos, the invagination begins immediately on the shell edge. Bartos does not indicate any color.