Diagnosis: test round, lenticular or pyriform, a highly flexible, colorless, hyaline membrane that follows the size changes of the cytoplasma during feeding or starvation; aperture usually between folds and flexible; plasma fills the test completely; nucleus vesicular or ovular; filopodia usually few, long and straight, branching and anastomosing.
Dimensions: mostly small species.
Ecology: common in different types of water; feeding on algae and bacteria.
Remarks: Nucleus and pseudostome are difficult to observe, the latter is usually a small hole between folds.
Four observed species: