Genus: Cell body cylindroid, both ends rounded; cell wall smooth or granulated or longitudinally lined; constriction or bands present in some species; outer cell wall yellowish or brownish; chloroplast has radially-arranged laminae which attached cell wall in full length; one or several pyrenoids in each semicell, aligned in chloroplasts (Illustrations of The Japanese Fresh-water Algae, 1977).
Species: Cell body cylindrical, medium in size, slightly constricted at the center, (56-65)-80 μm long, 20-31 μm wide, L/W=2-2.5; cell wall transparent or slightly brownish (Illustrations of The Japanese Fresh-water Algae, 1977).
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Cell wall lined 
P. spirostriolatum
210 x 22 μm
near Omine-numa
Minakami
Gunma, 2006
P. spirostriolatum
173 x 23 μm
Ko-numa 2
Minakami
Gunma, 2008
P. spirostriolatum
240 x 20 μm
Tane-ike
Togakushi highland
Nagano, 2006
P. spirostriolatum
222 x 26 μm
Iyari marsh 1
Omachi
Nagano, 2007
P. spirostriolatum
202 x 23 μm
Ohnuma
Nasu-shiobara
Tochigi, 2007
