Subgenus: Eustaurastrum
Section: Processiformes
Family: Cell wall with 2 or more partitions
Subfamily: Cell division occurs at central constriction
Genus: Cell body short, radiate in shape; apical view of the cell, triangular, polygonal, ellipsoidal or spindle-shaped; zygospores formed outside of mother cells.
Subgenus: with arm-like projections (Illustrations of The Japanese Fresh-water Algae, 1977)
Section: Arm-like projections granulated or dented
2 arm-like projections 
S. leptocladum
43 x 98 μm
USA, 1999
S. playfairi ?
or biexcavatum ?
27 x 85 μm
Otto-Numa
Ibaraki, 2002
S. playfairi ?
or biexcavatum ?
x 60 μm
Kejo-numa 1
Osaki
Miyagi, 2006
S. johnsonii
4 samples
2005-2008
S. subparvulum ?
3 samples
10-22 μm
2001-2007
S. biexcavatum
8 samples
1999-2008
S. tetracerum ?
6 samples
10-22 μm
2001-2007
S. iotanum
or S. tetracerum ?
18 samples
2- or 3-arms
19-29 μm
2001-2007
Staurastrum sp.
μm
Japan, 1998
Staurastrum sp.
μm
Higusa-numa
Hikari
Chiba, 2003
