Metromonas (met-row-moan-ass) simplex (Griessmann, 1913) Larsen and Patterson, 1990. Cells are obovate, 3 to 8 microns long (mostly 4 to 7 microns), 2 to 6 microns wide and dorso-ventrally flattened, and have smooth pellicle. The abflagellar margin of the cell is thicker than the (posterior) margin. Two flagella of very unequal length arise from the posterior part of the cell. The major flagellum is always present, is about 1.5 to 3.0 times the length of the cell and may be attached to the substrate. The short inactive flagellum is about 1 microns long and inserts to the right of the major flagellum. It may be difficult to see. The cells normally attach to the substratum and swing from side to side like a pendulum and the cells may also glide with the cell body in front of the flagellum. More common than M. grandis.