Cryptodifflugia fusca Penard, 1890
Basionym: Cryptodifflugia oviformis fusca Penard, 1890

Diagnosis: Differs from the typical form by its yellowish‑brown shell. Dimensions as in the typical form, with which it frequently co‑occurs. The taxon is polymorphous in both size and shape; elongated specimens are often recorded.

Dimensions: Shell length 13–26 μm; width 8–17 μm; aperture diameter 3–6 μm.

Ecology: Freshwater sediments; Sphagnum mosses; wet green mosses; aquatic plants; acid soils.

Distribution: Cosmopolitan.

References: Bobrov, A., Mazei, Y., 2017. A review of testate amoeba genus Cryptodifflugia Penard, 1890 (Phryganellina: Cryptodifflugiidae) with a key to species. Zootaxa 4282 (2): 292–308.

*) Taxonomic Note: Cryptodifflugia oviformis var. fusca Penard, 1890, is changed to Cryptodifflugia fusca Penard, 1890.
A formal change is not required in this case according to the International Code of Zoological Nomenclature:
(1) According to Article 45.6.3, as the name was published before 1961 using the abbreviation var., it is deemed to be subspecific rather than infra-subspecific and therefore falls under the rulings for species-group nominal taxa (Chapter 10).
(2) According to Article 46.1, names established at either species rank (species or subspecies) are simultaneously established at the other rank, with the same author and the same type. The authority thus remains unchanged.