Diagnosis: Shell oval or pyriform, rigid test without collar, densely or sparsely agglutinated with mineral xenosomes; xenosomes attached to the surface of the test, or embedded into and surrounded by a structureless, sheath like organic cement matrix; aperture may be circular and regularly agglutinated with xenosomes; it may have an organic rim, or it may be narrow and irregular; test not filled entirely by the cytoplasm; filopodia branching.
Type species: Pseudodifflugia gracilis Schlumberger, 1845.
Ecology: freshwater, soil and marine littoral sands.
Remarks: About 20 species, often with incomplete descriptions. Even the type species needs a much more accurate description: “ Animal test brown-bluish, encrusted and covered with small sand grains, ovoid, more or less elongated, with very long filipods”. That’s all, without any images.
Probably this genus is a “Sammelgruppe”, a taxon that contains a number of not closely related amoeboids. Some species may belong to the genus Plagiophrys, like P. compressa.
Key to some species:
| 1 | Shell compressed | |
| – | Shell not compressed | 2 |
| 2 | Shell < 25 µm | 3 |
| – | Shell > 30 µm | 5 |
| 3 | Aperture very small, c. 4-5 µm | P. microstoma |
| – | Aperture larger | 4 |
| 4 | Shell ovoid, without a neck | |
| – | Shell ovoid, tapering to a small distinct neck | P. spec. |
| 5 | Shell densely covered with xenosomes | 6 |
| – | Shell loosely covered with xenosomes | |
| 6 | Plasmabody fills the shell completely | |
| – | Plasmabody doesn’t fill the cell completely |
