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: Cell body oblong with both ends rounded, 15-35 μm long, 4.5-5.8 (-9) μm wide; cells arranged in a linear series contacting nearly with their entire sides; outer cells with a long curved spine at each ends, sometimes inner cells with a long spine at one pole; cell wall smooth or covered with linear microgranules (Photomicrographs of the Freshwater Algae, vol. 17, 1996).
S= length of Spines; L=Body length; W=Body width (terminal cells)
Google Image Search
L/W = about 3, terminal cells spindle-shaped 
var. maximus
cell 45 x 15 μm
L/W=3.0
S/L=0.6
Umi-no-nakamichi
Fukuoka, 2001
var. maximus ?
cell 37 x 11 μm
L/W=3.4
S/L=1.0
Japan, 1997
var. maximus ?
cell 36 x 12 μm
L/W=3.0
S/L=0.7
Chiba-Minato Park
Chiba, 2003
var. maximus ?
cell 35 x 13 μm
L/W=2.7
S/L=0.6
Chiba-Minato Park
Chiba, 2003
var. maximus
cell 32 x 11 μm
L/W=2.9
S/L=0.6-0.9
Koga museum
Koga
Ibaraki, 2003
var. maximus
cell 26 x 8.5 μm
L/W=2.4-3.1
S/L=0.6
Japan, 1998
S. maximus
stock Tsh-1
cell 20 x 8 μm
L/W=2.5
S/L=0.8
Showa Memorial p.
Tokyo, 2001
var. maximus ?
cell 24 x 8 μm
L/W=
Hasu-ike
Shiga highland
Nagano, 2005
