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 Closterium; cell wall mostly dotted, but with spines or other patterns in some species (Illustrations of The Japanese Fresh-water Algae, 1977). Species:

100 μm 200 μm 300 μm; x 200 : 50 μm 100 μm 150 μm; x 400

Images of collecting locality: Kamitashiro, Oze-ga-hara (Oze marsh), Katashina village, Gunma Pref., Japan, June 29, 2006 by Y. Tsukii