Cryptodiffflugia crenulata Playfair, 1917
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; my measurements 15-18 µm.
Ecology: Fresh water, on waterplants. Not rare.