Genus: Body blunt at rear; kineties spiralled when body contracts (Illustrated Guide, 1985).
Species: cell body 400-600 μm; macronucleus moniliform (Kudo, 1966). 600 μm long (without expansion or attenuation); peristome 1/2 body length; macronucleus moniliform; size and the length of the peristome separate this species from S. ambiguum (1-3 mm long, peristome 2/3 the body length) (Carey, 1992).