Genus: Cilia in groove, opening to right; margins smooth; body kineties complete (Illustrated Guide, 1985). Usually ovoid, ventral surface flattened; dorsal domed and longitudinally ribbed with a cleft on the right lateral edge; a large podite with secretory canal posterior; somatic ciliation restricted to ventral surface; a large macronucleus central; two contractile vacuoles (Carey, 1992). Species: Cell body ovoid, 45 μm long (Carey, 1992).

31 μm 63 μm 94 μm; x 640

mages of collecting locality: Kawaguchi Natural Park, Sashima, Kawaguchi city, Saitama Pref., Japan, February 5, 2006 by Y. Tsukii

Dysteria navicula Kahl, 1928: Ovoid, elongate, up to 35 μm long; no ribs on dorsal surface; but cleft on the right very wide; similar to D. calkinsi but longer in the body (posterior end slightly tapered); a single macronucleus and two micronuclei (Carey, 1992).

* Dysteria calkinsi (Calkins, 1902) Kahl, 1931: Ovoid, 45 μm long; cleft on the right of the body very wide in anterior; cytopharyngeal apparatus simple; six macronuclei and two contractile vacuoles (Carey, 1992).