Genus: Cell body short, radiate in shape; apical view of the cell, triangular, polygonal, ellipsoidal or spindle-shaped; zygospores formed outside of mother cells (Illustrations of The Japanese Fresh-water Algae, 1977). Species [ var. irregulare ]: Unicells, planktonic; cell body flat, subpyramidate, 10-17 μm long; two sides shallowly and the other two sides deeply concave; angles tapered into long, straight or slightly curved spines (10-29 μm long); cell wall smooth; a single chloroplast plate-like, with a pyrenoid (Photomicrographs of the Freshwater Algae, vol. 17, 1996).

Similar genus -->> Tetraedriella (Xanthophyceae); Goniochloris (Xanthophyceae);

31 μm 63 μm 94 μm; x 640

T. incus var. incus: Unicells, planktonic; cell body flat, quadrangular in shape, 5-12 μm long; two sides shallowly and the other two sides deeply concave; angles tapered into long, straight spines (5-15 μm long); cell wall smooth; a single chloroplast plate-like, with a pyrenoid (Photomicrographs of the Freshwater Algae, vol. 17, 1996).

* T. incus var. irregulare: Unicells, planktonic; cell body flat, subpyramidate, 10-17 μm long; two sides shallowly and the other two sides deeply concave; angles tapered into long, straight orslightly curved spines (10-29 μm long); cell wall smooth; a single chloroplast plate-like, with a pyrenoid (Photomicrographs of the Freshwater Algae, vol. 17, 1996).