Difflugia viscidula Penard, 1902
Diagnosis: shell elongated oblong, without a slight constriction between body and neck; neck, if distinct, short and composed of much smaller particles than the rest of the shell; neck sometimes with concave sides, like a vase. With zoochlorellae.
Dimensions: Penard (1902): 180-260 µm; my measurements length: 222-460 µm (mean 365 µm); width 118-200 µm; aperture 56-101 µm.
Ecology: fresh water; the Netherlands (Naardermeer and several other locations).
Remarks: a caracteristic species.