(het-err-owe-knee-ma) ovale Kahl, 1928. Cell outline is ovate. Cells are 15 to 30 microns, flattened, and metabolic. The pellicular striations follow a S-helix on the ventral and dorsal faces of the cell and may or may not have associated refractile bodies. This species is capable of vigorous squirming movements. Two flagella are of almost equal length and are slightly longer than the cell. The posterior flagellum has a knob at its base and is stronger than the anterior flagellum. The ingestion organelle has two rods, and the species eats diatoms. The reservoir and nucleus are located in the left side of the cell. The cells move by skidding or by vigorous squirming in contact with substrate. Sometimes commonly observed.