Genus Thecamoeba Fromentel, 1874
Diagnosis: Locomotive form, usually between 30 and 350 µm long, flattened and oblong in outline, often with several parallel folds or wrinkles. Anterior edge semi-circular with an extensive hyaloplasm that can occupy more than half the cell. Posterior edge often slightly convex, sometimes with a knob uroid. Form of the nucleus is an important diagnostic feature for delineating species, and thecamoebae can have a single spherical or ovoidal nucleus with a central nucleolus, granular nucleolus, or nucleolus as 2 or 3 parietal pieces. Cytoplasm may have crystals and contractile vacuoles. No cysts known.
At the ultrastructural level, nuclear envelope without an internal fibrous lamina and cell coat as a thick, dense, amorphous, glycocalyx.
Type species: Thecamoeba quadripartita Fromentel, 1874
Ecology: described from freshwater, terrestrial, and marine habitats.
Remarks: Common genus with 18 described species.