Family: Paoral membrane prominent, may be large and may project stiffly (Carey, 1992). Genus: Ovoid to ellipsoid; peristome begins at anterior end and extends for 2/3 the body length; a conspicuous membrane at both edges; one to many posterior stiff sensory cilia (Kudo, 1966). Swimming as leaping movement. Species:

Similar Genus ->> Uronema; Cyclidium

50 μm 100 μm 150 μm; x 400

* Pleuronema marinum Dujardin, 1841: Elongate, ovoid; about 50 ciliary rows; 51-126 μm long; salt water (Kudo, 1966). Very common; ovoid or elongate in shape, 100 μm long; undulating membrane (velum) long, running from anterior almost to posterior where cytostome lies in a deep pocket; somatic ciliation uniform; caudal cilia present; a single ovoid macronucleus; large posterior contractile vacuole; numerous trichocysts; 40-55 kineties (Borror, 1965) (Carey, 1992).

Pleuronema coronatum Kent, 1880-1882 (Syn. Pleuronema coronata var. marina Kahl, 1928): Very common; ovoid, slightly reniform; 90 μm long; undulating membrane (velum) very large, running from anterior almost to posterior; caudal cilia present; a single ovoid macronucleus; large contractile vacuole; trichocyst large but few in number (Carey, 1992).

Pleuronema crassum Kahl (Syn. Pleuronema chrysalis (Ehrenberg, 1838) Kahl, 1931): 100 μm long; Ovoid; long peristome with large undulating membrane; uniformly long cilia on body; marine (How to know the protozoa, 1979). Cell body ovoid with the anterior wider than the posterior, 60-80 μm long; undulating membrane (velum) very large; trichocysts present; a single spherical macronucleus; no caudal cilium (Carey, 1992).