Pseudodifflugia fulva  Archer, 1870 (sensu Penard, 1902)

Diagnosis: Shell ovoid and rarely subspherical, circular in cross‑section, rigid and chitinoid. Colour pale yellow, becoming golden‑yellow to brown with age. Surface covered with small, flat, siliceous, transparent scales scattered irregularly; occasionally larger angular quartz fragments are attached. In some individuals the scales are replaced by small diatoms (4–5 µm), sharply delimited. Aperture perfectly rounded, its diameter generally about half that of the shell. Plasma rounded, not filling the entire internal cavity, clear, with a spherical nucleus bearing a central nucleolus and a contractile vacuole near the nucleus. Pseudopodia extremely fine and elongated, sometimes thicker or temporarily swollen by currents of plasma; despite their delicacy they attach the organism firmly to the substrate.

Dimensions: shell length 15–23 µm (mean ~17 µm).

Ecology: freshwater.