Clautriavia cavus Lee and Patterson, 2000. Cell outline is oval to oblong. Cells are 7.5 to 10 microns long, flattened and rigid. One flagellum directed posteriorly emerges from a ventral subapical depression, is about 1.5 to 2 times the length of the cell and makes close contact with the substrate when the cell is gliding. The cells have a shallow, wide ventral groove, which is easy to overlook. The ventral face of the cell appears to be slightly concave. The cell surface may be rather warty and food particles are seen in the posterior part of the cell. The cells glide slowly and smoothly with the posterior part slightly raised above the substrate. Often observed, but not in large numbers.