Pyxidicula patens – 39 µm
Genus Pyxidicula Ehrenberg, 1838
Diagnosis: Shell hemispherical, bowl-shaped; the aperture is almost as wide as the diameter of the shell, apertural rim usually recurved outside (Fig. 11). Shell wall areolate, composed of organic, hollow building units, which in older, brown specimens become tilled with inorganic material like manganese, One vesicular nucleus. During mitosis the nuclear membrane and the nucleolus remain intact with an intranuclear spindle apparatus (closed orthomitosis). One contractile vacuole. Feeding on algae and bacteria. Habitat: freshwater plants.
Pyxidicula operculata – drawing by Hoogenraad & De Groot, 1940