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. abundans ]: Colonies of 4 cells arranging lineary; cell body ovoid or ellipsoidal in shape, 9-20 μm long, 3-5 μm wide; outer cells with long spines at both ends (6-8 μm long) and short spines at outer side (3-5 μm long); inner cells sometimes have a short spine at both ends (Illustrations of The Japanese Fresh-water Algae, 1977).

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Outer cells have spiny projections and lateral spines
var. abundans a dividing cell cell 9 x 3 μm Ueno Tokyo, 2001	var. abundans cell 8 x 4 μm Soka Saitama, 2002	var. abundans cell 10 x 4 μm Saitama, 1999	var. abundans cell μm Kamihira Park Ageo Saitama, 2003
var. abundans cell μm Hagoromo Park Chiba, 2003	var. abundans cell 9 x 4 μm Shiroyama p. Okegawa Saitama, 2006	var. abundans cell 9 x 4 μm Kanayama g. p. Kiyose Tokyo, 2006	var. abundans cell 10-11 x 3.5 μm Heisei-no-mori Kawajima Saitama, 2006
var. abundans ? cell 8 x 2.5 μm Mizumoto park Tokyo, 2001	var. abundans ? cell 10 x 4 μm Kayoicho-ike Fukuoka, 2001
Both spiny projections and lateral spines of outer cells elongated
var. longicauda or var. abundans ? cell μm Chiba-Minato Park Chiba, 2003	var. longicauda cell 9-10 x 3 μm Kayoicho-ike Fukuoka, 2001	var. longicauda cell 9 x 3 μm Koriyama Fukushima, 2001	var. longicauda cell μm route 272 Minakami Gunma, 2007
Outer cells have many short lateral spines
var. spicatus cell 9-10 x 3 μm Bessho-numa Saitama, 2001	var. spicatus cell 7 x 2.5 μm Umi-no-nakamichi Fukuoka, 2001
Cell body ovoid, small; both spiny projections and lateral spines are short
var. brevicauda cell 8 x 2.5 μm Japan, 1998	var. brevicauda cell μm Kiyose Tokyo, 2003	var. brevicauda cell μm spines μm Kanayama Green Park Tokyo, 2003	var. brevicauda cell μm spines μm Kodaira Central Park Tokyo, 2003
var. brevicauda or S. microspina ? cell μm spines μm Kayoicho-ike Fukuoka, 2001

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