Genus: Cell body small, length = width, strong constriction at its center; semicells inverted triangular, ellipsoidal, rectangular, etc. in shape; straight or slightly curved spiny projections at each corner; one pyrenoid in each semicell; cell wall smooth (Illustrations of The Japanese Fresh-water Algae, 1977).
Species: (Illustrations of The Japanese Fresh-water Algae, 1977).
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var. extensus:
A. extensus ?
v. extensus
15 x 15 μm
Yahei-daira m.
Yonezawa
Yamagata, 2007
A. extensus
v. extensus
μm
Kannon-numa
Shimogo
Fukushima, 2008
A. extensus ?
v. extensus
μm
Fujimitashiro
Katashina
Gunma, 2007
A. extensus
v. extensus
15 x 27 μm
Okubo Ryoke
Akigase park
Saitama, 2005
A. extensus
18 x 23 μm
Tanohara marsh
Shiga highland
Nagano, 2004
A. extensus
v. extensus
18 x 29 μm
Nozomiko
Iiyama
Nagano, 2007
A. extensus
v. extensus
18 x 31 μm
Tanohara marsh 1
Shiga highland
Nagano, 2007
A. extensus
v. extensus
17 x 17 μm
Tanohara Natural p.
Ontake highland
Nagano, 2005
A. extensus
v. extensus
μm
Chigo-ike m.3
Shiga highland
Nagano, 2008
A. extensus
v. extensus
16.5 x 15 μm
Kodanuki marsh
Fujinomiya
Shizuoka, 2006var. elongatus:
A. extensus
v. elongatus
17 x 13 μm
Tane-ike
Togakushi highland
Nagano, 2005
A. extensus
v. elongatus
26 x 24 μm
Shimo-no-koike
Shiga highland
Nagano, 2004
A. extensus
v. elongatus
19 x 17 μm
Karakemi marsh
Omachi
Nagano, 2006
A. extensus
v. elongatus
μm
Water reservoir
Iiyama
Nagano, 2008