Subgenus: lacks arm-like projections
Section [ Stellatiformes ]: Semicells with lines of spines (Illustrations of The Japanese Fresh-water Algae, 1977)
Species [ var. forficulatum ]: Cell body medium in size, 40-47.6 μm long, 37-60 μm wide (excluding spines), marginal projections present at both anterior and posterior sides of semicells, corner projections with dichotomous spines.
[ var. verrucosum ]: Cell body 39-45 μm long, 37-42 μm wide (excluding spines) corner projections with trichotomous spines (Illustrations of The Japanese Fresh-water Algae, 1977)

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var. forficulatum:
v. forficulatum 30 x 27 μm Tashirodaira m. Hakkoda mountain Aomori, 2006	v. forficulatum 38 x 30 μm Kejo-numa 2 Osaki Miyagi, 2006	v. forficulatum ? 35 x μm Miyatoko m.5 Minami-Aizu Fukushima, 2008
var. verrucosum:
v. verrucosum μm Chokai mt. Yuri-Honjo Akita, 2008	v. verrucosum 49 x μm Ko-numa 2 Minakami Gunma, 2008	v. verrucosum μm Senjo-ga-hara Nikko Tochigi, 2003
v. verrucosum ? 50 x 40 μm Ikenokochi marsh Tsuruga Fukui, 2004	v. verrucosum ? x μm Kannon-numa Shimogo Fukushima, 2008
v. verrucosum μm Oyomi marsh Hakuba Nagano, 2004	v. verrucosum 40 x 30 μm Maimeno-ike Norikura highland Nagano, 2006	v. verrucosum 45 x 33 μm Dojo-ike Norikura highland Nagano, 2006	v. verrucosum μm Dojo-ike Norikura highland Nagano, 2007
v. verrucosum μm Mi-ike 1 Norikura highland Nagano, 2007	v. verrucosum or S. hantzii ? μm Numappara m.2 Nasu-shiobara Tochigi, 2007
var. ?? or S. senarium ?
v. forficulatum ? or S. senarium ? 29 x 25 μm Kenashitai Hakkoda mountain Aomori, 2005	v. forficulatum ? or S. senarium ? 26 x 20 μm Iroha-numa Zao mountain Yamagata, 2005	v. forficulatum ? or S. senarium ? ?? x 30 μm Iroha-numa Zao mountain Yamagata, 2006
v. forficulatum ? or S. senarium ? 30 x 25 μm Ushidome-ike Norikura highland Nagano, 2005	v. forficulatum ? or S. senarium ? 28 x 27 μm Ushidome-ike Norikura highland Nagano, 2005	v. forficulatum ? or S. senarium ? 33 x 33 μm Ushidome-ike Norikura highland Nagano, 2006	v. forficulatum ? or S. senarium ? 25 x 22 μm Azami-ike Norikura highland Nagano, 2006
v. forficulatum ? or S. senarium ? ?? x 30 μm Karakemi marsh Omachi Nagano, 2006	v. forficulatum ? or S. senarium ? 23 x 20 μm Watasuge marsh Tsugaike highland Nagano, 2006

Similar species -->> S. senarium (smaller than S. forficulatum; about 30 μm excluding arms);

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