Cyclopyxis arcelloides (Penard, 1902) Deflandre, 1929
Diagnosis: Test hemispherical, brownish, thin, chitinous, covered with small flat mineral particles; pseudostome slightly invaginated, aperture about half the test diameter.
Dimensions: Diameter 100-110 µm.
Ecology: Freshwater, Sphagnum, submerged mosses. Probably cosmopolite.
Remarks: Van Oye (1951) describes a variety minima with a diameter of 40 µm.