Genus: Variable in shape; strong constriction at center; semicell ellipsoidal, polygonal, etc.; cell wall with simple or branching spines, most of them laterally aligned; 4 plate-like chloroplasts in each semicell; one or more pyrenoids in each chloroplast (Illustrations of The Japanese Fresh-water Algae, 1977). Species (var. fasciculatum): Cell body (without spines) (42-48)-54 μm long, 34-39 μm wide, isthmus (11)-13 μm wide, semicells with two anterior, two lateral, one basal spines, without central bulging, (Illustrations of the Fresh-water Algae, 1977).

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640

Xanthidium fasciculatum Ehrenberg var. fasciculatum: Cell body (without spines) 44-(67) μm long, 44-59 μm wide, isthmus 12-21 μm wide, semicells with two anterior, two lateral, two basal spines (Illustrations of the Fresh-water Algae, 1977).

Xanthidium cristatum var. leiodermum (Roy et Bisset) Turner: Cell body (without spines) (42-48)-54 μm long, 34-39 μm wide, isthmus (11)-13 μm wide, semicells with two anterior, two lateral, one basal spines, without central bulging, (Illustrations of the Fresh-water Algae, 1977).