Thecamoeba striata (Penard, 1890) Schaeffer, 1926
Diagnosis: Stationary amoebae knobby but very little or not at all wrinkled; in locomotion flattened, oblong or elongately elliptical in outline, with broadest point usually just anterior to middle of amoeba and with posterior end usually broadly rounded; several parallel dorsal folds extending far anteriorly common in locomotive form; hyaloplasm an antero-lateral crescent sometimes extending three-quarters of length posteriorly; nucleus with two, three, occasionally more nucleolar pieces arranged peripherally; a single contractile vacuole, highly deformable, with diameter to about 12.5 µm.
Dimensions: length approximately 28-78 µm (mean 48-52 µm), with length: breadth ratio approximately 1.1-3.4 (mean 1.4-2.0); nucleus 6.5-10.0 µm (Page, 1977).
Remarks: this species is most likely to be confused with T. quadrilineata. It might also be confused with T. similis, since cells of the latter species in a preparation with few bacteria may take an elongated, rather smooth locomotive form with a few dorsal striae. However, T. similis is likely in a short time to pass into a more characteristic form.