Genus: Colonies of 4 (or 2, 8, 16) cells attached side by side, arranged linearly or zigzag; cell body elliptical or spindle or crescent in shape; terminal cells with spiny projections in many species; cell wall usually smooth, but in some species granulated or dented or ridged (Illustrations of The Japanese Fresh-water Algae, 1977).
Species: Colonies of 2, 4 cells arranging linearly; cell body ellipsoidal, both ends rounded, 8-13 μm long, 2-4.5 μm wide; outer cells with a spiny projection (3-13 μm long) at one end (Illustrations of The Japanese Fresh-water Algae, 1977).
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S. bicaudatus
8 cells
9 x4 μm
L/W=2.3
S/L=0.7
Japan, 1998
S. bicaudatus
4 cells
13 x 3.5 μm
L/W=3.7
S/L=0.9
Sue-machi
Japan, 2000
S. bicaudatus
2 cells
11 x 4 μm
L/W=2.8
S/L=0.9
Sue-machi
Fukuoka, 2001
S. bicaudatus ?
1, 2 cells
11 x 4 μm
L/W=2.8
S/L=1.0
Koshigaya
Saitama, 2001
S. bicaudatus ?
stock Skg-23
1 cells
11 x 5 μm
L/W=2.2
S/L=0.8
Kawagoe
Saitama, 2001
