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 [ var. quadricauda ]: Colonies of 2, 4 or 8 cells arranging linearly; cell body elongated ellipsoidal, 11-18 μm long, 3.5-7 μm wide; terminal cells with long spiny projections (10-17 μm long); cell wall smooth (Illustrations of The Japanese Fresh-water Algae, 1977).
S= length of Spines; L=Body length; W=Body width (terminal cells)

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L/W = about 3, terminal cells spindle-shaped
var. quadricauda cell 23-27 x 8 μm L/W= Shiba river near Owada Park Saitama, 2005	var. quadricauda or S. longispina ? cell 18 x 5.5 μm L/W=3.3 S/L=1.2 Kuroiso Tochigi, 2001	var. quadricauda or S. longispina ? cell 16 x 6 μm L/W=2.7 S/L=1.6 riverside park Abukuma river Fukushima, 2005	var. quadricauda dividing cells cell 17 x 6 μm L/W=2.8 S/L=1.0 Koshigaya Saitama, 2001
var. quadricauda cell 18 x 6 μm L/W=3 S/L=1.1 Nanbata castle p. Fujimi Saitama, 2005	var. quadricauda cell 28 x 8 μm L/W=3.5 S/L=0.9 Japan, 1999	S. quadricauda cell 17 x 6.5 μm L/W=2.6 S/L=1.1 Itakura Gunma, 2003	S. quadricauda cell 28 x 10 μm L/W=2.8 Showa-machi G.P. Showa Saitama, 2003
S. quadricauda cell 16.5 x 5.5 μm L/W=3.0 Tane-ike Togakushi highland Nagano, 2005	S. quadricauda spines thick cell 20 x 6 μm L/W=3.3 O-ike park Yabuki Fukushima, 2003	S. quadricauda spines thick cell 18 x 7 μm L/W=2.6 S/L=1.1 Tsukuba Ibaraki, 2002	S. quadricauda spines thick cell 17 x 6-7 μm L/W= kenko-fukushi m.p. Koshigaya Saitama, 2005
Spines straight
var. quadricauda stock Sak-6a cell 14 x 4.7 μm L/W=3.0 S/L=0.6 Asaka Saitama, 2000	var. quadricauda cell division cell 17 x 6 μm L/W=2.8 S/L= 1998-2000	var. quadricauda ? 2-cells type cell 15 x 5 μm L/W=3.0 S/L=0.8 Japan, 1998-99	var. quadricauda cell 10 x 3 μm cell 16 x 6.5 μm L/W=3.3, 2.5 Tochigi, 2001
var. quadricauda cell 10 x 3 μm L/W=3.3 Kodama town Saitama, 2003	S. quadricauda cell 16 x 5.5 μm L/W=2.9 S/L=0.85 Uruguay, 1999	S. quadricauda v. parvus ? cell 11 x 3 μm L/W=3.7 S/L=0.64 Tatebayashi Gunma, 2001	S. quadricauda dividing cells 12-14 x 4-5 μm L/W=2.8-3 S/L=0.83-1.1 Tokyo, 2001
S. quadricauda cell 18 x 5 μm L/W=3.6 S/L=0.89 Koshigaya Saitama, 2001	S. quadricauda stock Skg-22,23 L/W=2.4 S/L=0.65 Kawagoe Saitama, 2001	S. quadricauda v. parvus ? L/W=2.4 S/L=0.67 Wan-park-land Kochi, 2002	S. quadricauda cell 19 x 7 μm L/W=2.7 S/L=0.79 Showa Memorial p. Tokyo, 2001
S. quadricauda cell 15 x 5.5 μm L/W=2.7 Daidarabotchi-ike Iizuna-kogen Nagano, 2003	S. quadricauda cell 15 x 5 μm L/W=3.0 Lake Shirakaba Tateshina & Chino Nagano, 2005	var. quadricauda cell 25 x 7.5 μm L/W=3.3 S/L=1.0 Japan, 1998
v. biornatus 10 samples cell μm 1999-2006	S. quadricauda cell 19 x 7 μm L/W=2.7 Iruma river Kawagoe Saitama, 2004
L/W = about 4; cell body elongated
var. quadricauda ? cell 25 x 7 μm L/W=3.6 S/L=0.9 Koriyama Fukushima, 2001	var. quadricauda ? cell 23 x 6 μm L/W=3.7 S/L=0.7 Otto-Numa Tsuchiura Ibaraki, 2002	var. quadricauda ? cell 21 x 5.5-7 μm L/W= S/L= near Imori pond Myoko highland Niigata, 2004	var. quadricauda cell 26 x 6 μm L/W=4.3 S/L=1.0 Japan, 1997
var. quadricauda cell 14 x 3 μm L/W= S/L= near Yamaguchi Univ. Yamaguchi, 2004
Others
S. quadricauda cell 19 x 5 μm L/W=3.8 S/L=1.1 Japan, 1998	S. quadricauda cell 15 x 4.5 μm L/W=3.3 Nanbata castle p. Fujimi Saitama, 2005	S. quadricauda cell μm Michi-no-eki Tsukiyono Gunma, 2003	S. quadricauda cell μm O-ike park Yabuki Fukushima, 2003
var. westii ? 7-9 x 3.5-4 μm L/W=2.0-2.3 S/L=0.7-0.9 Japan, 1998	abnormals ?? 8-9 x 1.5-2 μm L/W=4.5-5.3 S/L=0.8-0.9 Japan, 1998	S. quadricauda ? with small projec. cell 11 x 4.7 μm L/W=2.3 S/L=0.6 Saitama, 2001	S. quadricauda ? with small projec. or S. quadrispina ? cell 16 x 6 μm L/W=2.7 Chiba-Minato Park Chiba, 2003
S. quadricauda ? or S. bicaudatus ? cell μm L/W= Kanayama Green Park Kiyose Tokyo, 2003	S. quadricauda ? cell μm L/W= Higusa-numa Hikari Chiba, 2003	S. quadricauda ? cell 13 x 6.6 μm L/W=2.0 S/L=0.7 Tochigi, 2001	S. quadricauda ? with small projec. cell 9 x 4 μm L/W=2.2 S/L=1.0 Nagano, 2001
S. quadricauda ? with small projec. cell 10-12 x 4 μm L/W=2.5-2.8 Kusatsu Onsen b.t. Kusatsu Gunma, 2005	S. quadricauda cell μm L/W= Chiba-Minato Park Chiba, 2003	S. quadricauda outer 18 x 5.5 μm inner 17 x 5.5 μm L/W=3.1, 3.3 Iruma Park Iruma Saitama, 2005	S. quadricauda cell 12 x 3.5 μm L/W=3.4 Hasu-ike Shiga highland Nagano, 2005
S. quadricauda cell 14 x 5 μm L/W=2.8 riverside park Abukuma river Fukushima, 2005	S. quadricauda cell 15.5 x 5.5 μm L/W=2.8 Tsutsuji-ga-oka Tatebayashi Gunma, 2006	S. quadricauda cell 11 x 4.5 μm L/W=2.4 Yoshino park Mitsukaido Ibaraki, 2006

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