Family & Genus: Under 100 μm long; oblong to ovate; with several, longitudinal, parallel ridges; uninucleate . Species: Cell body 35-38 μm long; elliptical; 2-5, usually 4 dorsal ridges; nucleus with single, smooth endosome (How to know the protozoa, 1979).

Similar species ->> Thecamoeba striata

S. munda Penard, 1890: Locomotive, 40-50 μm long, 30-40 μm wide; pseudopods none; uroid none; ectoplasm, pale, as anterolateral margin; 3-4 dorsal ridges; endoplasm finely granular; nucleus spherical 10 μm, endosome ring between 2 polar caps; contractile vacuole none ? (Illustrated Guide, 1985).

S. similis (Schaeffer, 1926): 30-80 μm long; broadly ovate, with few dorsal ridges; nuclear endosomal granules scattered under nuclear membrane (How to know the protozoa, 1979).

S. quadrilineata: 35-38 μm long; elliptical; 2-5, usually 4 dorsal ridges; nucleus with single, smooth endosome (How to know the protozoa, 1979).

S. striata (Penard, 1890): Locomotive, 30-50 μm long, 20-30 μm wide, pseudopods rare; uroid none; ectoplasm pale; 3-5 dorsal ridges and clear, antero-lateral margin; endoplasm finely granular; nucleus spherical, 5-6 μm, endosome as a band or 2-3 pieces; contractile vacuole 8-12 μm (Illustrated Guide, 1985). Ovate; 30-80 μm long; 3-4 dorsal ridges; nucleus with 2 or 3 ribbon-like endosomes (How to know the protozoa, 1979).

S. corrugata : 35-80 μm long; usually 6 ridges; slightly tapered front and rear; nucleus with plastic central endosome (How to know the protozoa, 1979).