Family: Frontal cirri differ in size and/or pattern from ventral ones of files; "collar" extends short distance along right edge of body; oral area not U-shaped (Illustrated Guide, 1985). Genus: Elongate body drawn out into a tail-like portion; 3 frontals; 2-4 rows of ventral cirri; marginals; no transverse cirri; sometimes rose- or violet-colored (Kudo, 1966). Frontventral cirri in zig-zag files; rear half narrowed, tail-like (Illustrated Guide, 1985). Species:

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640

* Uroleptus lamella (Ehrenberg, 1831) Borror, 1972 (Syn. Uroleptus rattulus Stein, 1859): Elongate, vermiform with a small rounded anterior and long flexible tail; 300 μm long; buccal area and AZM small (Carey, 1992).

Uroleptus lacteus (Kahl, 1930-5) Borror, 1972 (Syn. Parauroleptus lacteus Khal, 1930-5): Body elongate, divided into three distinct regions (head, trunk, tail); tail region lacks long cirri; 200 μm long; AZM 1/4 of the body length; two ovoid macronuclei; lateral stiff cilia present (Carey, 1992).

Uroleptus limnetis Stokes: About 200 μm long; lateral stiff cilia present; 4 rows of ventral cirri (2 marginal); long caudal cirri present; fresh water among vegetation (Kudo, 1966).

Uroleptus caudatus (Claparède and Lachmann, 1858) Kahl, 1930-5 (Syn. Oxytricha caudatus Claparède and Lachmann, 1858): Body elonagte, divided into three distinct regions (head, trunk, tail); AZM 1/4 of the body length; transverse cirri very small; two ovoid macronuclei; tail region lacks long cirri; size not given; lateral stiff cilia absent (?) (Carey, 1992).

Uroleptus longicaudatus Stokes: About 200 μm long; marsh water with sphagnum (Kudo, 1966).

Uroleptus piscis (Müller, 1786) Ehrenberg, 1831: 400 μm long; tail region has long cirri; two ovoid macronuclei (Carey, 1992).