Cyclopyxis kahli (Deflandre, 1929)
Diagnosis: Shell brown, usually circular in ventral and dorsal view, very rarely slightly elliptical, hemispherical in lateral view; lateral sides evenly rounded, in large size class sometimes almost parallel, making shells barrel shaped; dorsal side usually slightly flattened and often very uneven by large, protruding assortment of mineral particles; greyish to dark-brown, opaque; composed of xenosomes more distinct and rough on dorsal surface than on smoother ventral half, which appears covered by thin, organic layer. Pseudostome in or near centre of ventral surface, distinctly and evenly invaginated, perfectly or roughly circular, with edge completely or partially covered by rather regularly arranged, roundish xenosomes ("dents") in about 60% and 10% of specimens from small and large size class, respectively; often plugged by detritus giving impression of very deep pseudostome invagination.
Dimensions: Diameter of shell 77-105 µm; depth of shell 43-61; diameter of aperture 24-36 µm.
Ecology: mosses and Sphagnum.
Remarks: This species is similar to C. arcelloides (Penard, 1902) but differs from it in size and the diameter of the aperture.
Cyclopyxis kahli var. cyclostoma Bonnet & Thomas, 1960
Diagnosis: Pseudostome edge without specialized xenosomes.
Dimensions: Shell diameter 80-100 µm; shell depth 50-60 µm; pseudostome diameter 12-30 µm.
Cyclopyxis kahli var. obliqua Decloitre, 1969
Diagnosis: Pseudostome oblique; possibly described from single, terratogenic specimen.
Dimensions: Shell diameter 75 µm; shell depth 50 µm; pseudostome diameter 25 µm.