Genus Phryganella Penard, 1902
Diagnosis: shell in lateral view hemispherical or higher; aperture large, often 2/3 of the shell diameter, not invaginated; shell composed of mineral particles of variable size, embedded in an organic matrix, which in older specimens can become dark brown due to manganese and iron deposition; around aperture and ventral surface these particles are small, giving it a regular and smooth outline while at the aboral extremity larger grains are incorporated; ovular nucleus; cyst internal with aperture closed by an organic diaphragm; pseudopodia lobose but slightly tapering, a little conical shaped.
Habitat: Feeding mainly bacteria, fungi and algae.
Remarks: based on empty shells Phryganella species are hard to distinguish from species as Difflugia globulosa and D. lithoplites (without spines) and Pseudodifflugia species. It is important to observe the shape of the pseudopodia, but living specimens are rare in samples. Keep wet mounts for some days in a moist chamber. Living specimens, if present, move to the cover glass.
Key to the species:
| 1 | Shell diameter < 150 µm | 2 |
| – | Shell diameter > 150 µm | P. nidulus |
| 2 | Shell diameter >= height | 3 |
| – | Shell diameter < height | P. paradoxa |
| 3 | Shell diameter > 17 µm | 4 |
| – | Shell diameter < 17 µm | P. microps |
| 4 | Shell diameter < 25 µm | P. dissimulatoris |
| – | Shell diameter > 25 µm | P. acropodia |
