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: Cells attached side by side along 3/4 of their side (arranging in 1 or 2 rows), inner spaces absent (cf. S. arcuatus); cell body ellipsoidal or ovoid without spiny or dented projections, 7-20 μm long, 4-10 μm in diam. (Illustrations of The Japanese Fresh-water Algae, 1977).
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v. ecornis ?
cell 16 x 5 μm
cell 16 x 4 μm
cell 12 x 2 μm
Japan, 1997
v. ecornis ?
cell μm
Mizuko
Fujimi
Saitama, 2003
v. ecornis ?
or S. minutus ?
stock Cka-2
Agricultural p.
Kashiwa
Chiba, 2002
v. ecornis ?
18 x 6-10 μm
near Ayu river
Fujioka
Gunma, 2004
v. ecornis ?
15 x 5-6 μm
Sagiyama m.p.
Saitama
Saitama, 2005
v. ecornis ?
12 x 11 μm
Kowashimizu
Suwa
Nagano, 2005
v. ecornis ?
13 x 3 μm
Ushidome-ike
Norikura highland
Nagano, 2005
v. ecornis ?
12 x 5 μm
Tanohara marsh
Shiga highland
Nagano, 2005
v. disciformis
or S. arcuatus ?
cell 12 x 6.5 μm
Kawashima
or Kawajima
Saitama, 2002
v. disciformis
or S. arcuatus ?
cell 11 x 5.5 μm
Kasama Park
Ibaraki, 2002
v. disciformis
or S. arcuatus ?
cell 9 x 5 μm
near Town Hall
Shobu
Saitama, 2004
v. disciformis
or S. arcuatus ?
cell 12 x 5 μm
Saitama, 1999
v. disciformis
or S. arcuatus ?
cell 11 x 5.5 μm
Uruguay, 1999
v. disciformis
or S. arcuatus ?
cell 11 x 6 μm
Dewa Park
Saitama, 2001
v. disciformis
or S. arcuatus ?
cell 8 x 5 μm
Nishi-Urawa
Saitama, 2001
v. disciformis
or S. arcuatus ?
cell 9 x 4.5 μm
Kabuto-yama
Nishi-no-miya
Hyogo, 2004
v. disciformis
or S. arcuatus ?
cell 10 x 6 μm
Kejo-numa 2
Osaki
Miyagi, 2006
v. disciformis
or S. arcuatus ?
cell 10-11 x 5-65 μm
Omotsubo marsh
Tetta-cho
Okayama, 2004
v. disciformis
or S. arcuatus ?
cell 9 x 3.5 μm
near Yamaguchi Univ.
Yamaguchi, 2004
v.disciformis
f . obiciturus ?
cell μm
Tsuki river
Ranzan
Saitama, 2003