Centropyxis cassis  (Wallich, 1864) Deflandre, 1929

Diagnosis: Shell is brown, ovoid; in outline the sides are usually parallel becoming semi-circular at the extremities. Shell in lateral view spherical in the aboral region and tapering towards the aperture. Shell composed of sand grains roughly arranged over most of the shell, except in the apertural region which appears smooth. This smoothness, unlike C. aerophila, is not due to a thick overlying layer of organic cement. The aperture is invaginated, oval, subterminal and has a pronounced rim.

Dimensions: Length 80-86 µm; height 50-73 µm.

Habitat: Freshwater and soil. Dry and submerged mosses.

Remarks: Possibly identical to C. constricta.