Cryptodiffflugia crenulata Playfair, 1917
Difflugiella crenulata in Grospietsch, 1964
Difflugiella crenulata in Schönborn, 1965

Diagnosis: shell ovoid, with truncate base, above which it is sometimes slightly constricted to form an obscure neck, end-view circular, crenelated; membrane smooth, thick, chitinous, hyaline or pale yellow, indented all over so as to appear broadly crenelated in optical section, both front and end; aperture circular, simple, slightly smaller than the base. Nucleus spherical. Cell sometimes with one or two large bipiramidal crystals.

Dimensions: Playfair length 17-20 µm, breadth 14-16 µm; other authors: shell length 15–20 μm, shell width 10–16 μm, aperture diameter 4 μm; my measurements: length 15-18 µm.

Ecology: Fresh water, submerged aquatic plants. Sphagnum mosses. Cosmopolitan. Not rare.