Genus: When extended, trumpet-shaped or cylindrical; highly contractile; some with mucilaginous lorica; conspicuous peristomal field frontal; contractile vacuole anterior-left; fresh water (Kudo, 1966).

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Cortical granules colourless, macronucleus band-form (vermiform or nodular)
S. roeseli 29 samples within lorica 360-1000 μm 1997-2008	S. roeseli 29 samples within lorica 360-1000 μm 1997-2008	S. roeseli 29 samples within lorica 360-1000 μm 1997-2008	S. roeseli 29 samples within lorica 360-1000 μm 1997-2008
Cortical granules colourless, macronucleus moniliform
S. polymorphus with symbionts 8 samples 220-1120 μm 1998-2008	S. muelleri without symbionts 8 samples 200-620 μm 1998-2008	S. muelleri ? without symbionts 8 samples 200-620 μm 1998-2008	S. pyriformis with symbionts 11 samples 230-340 μm 2001-2008
Cortical granules pigmented, green or blue-green
S. coeruleus 8 samples blue-green mac. moniliform μm 1999-2003	S. amethystinus 3 samples amethyst-blue oval mac. 120-430 μm 1998- 2005	S. multiformis 2 samples green oval mac. 109 μm Hiroshima, 1998
Cortical granules pigmented, pink or redish
S. igneus 10 samples oval mac. 152-460 μm 1998-2008	S. fuliginosus 21 samples oval mac. 230-340 μm 2005-2008
Misc.
Stentor sp. a dividing cell ? μm Japan, 1997