Genus: Cell body long cylindroid; a slight constriction at center; cross section of the semicells spherical,
slightly swell at the center but without a folded structure as
Docidium; slightly tapered toward both ends, which are truncated and smooth or
surrounded by granules or various small structures; laterally straight or wavy, with spiny
projections in some species; 2-10 ribbon-like chloroplasts in each semicell;
with many pyrenoids; a vacuole containing active granules at both ends same as in
cell wall mostly dotted, but with spines or other patterns in some species
(Illustrations of The Japanese Fresh-water Algae, 1977).
Species: Vegetative cells cylindrical, L/W = 11-18, constricted at center, 260- (384-616) -660 μm long, 24- (25-45) μm diam. (Illustrations of The Japanese Fresh-water Algae, 1977).