Family PERITROMIDAE Stein, 1867

Body ellipsoidal, dorsoventrally flattened, with regular ciliation on ventral surface only; lateral edges and dorsal surface bear short stiff spines, associated in latter location with curious wart-like prominences; buccal membranelles conspicuous at apical end of organism, curving down left side to cytostome located in anterior third of body; pair of ovoid-to-spherical macronuclei present; like hypotrichs (where formerly classified) in number of characteristics; generally in marine habitats, including salt marshes.

Peritromus Stein, 1862. Several species.