Sphenomonas angusta Skuja, 1956. Cells are 10 to 14 microns long, 4 to 7 microns wide, not flattened and with a dorsal groove. The cells are anteriorly obliquely truncated and posteriorly rounded. The cell bodies are slightly curved: the right margin of the cell is straighter than the left one. With two flagella, unequal in length, emerging from a relatively large flagellar pocket located in the right anterior end of the cell. The anterior flagellum is about 1.5 times cell length and its proximal part moves actively, the trailing posterior flagellum is less than 0.5 times the cell length. One large refractile inclusion often occupies the posterior part of the cell.
