Description of Petalomonas raiula:
Cells are about 8 20 microns long with a raised ventral groove, which extend from the collar around the flagella canal. The organism has thin lateral hyaline flanges. It has a wedge-shaped posterior end and a protrusion(s) on the posterior end of the cell. One emergent flagellum is about as long as the cell and is anteriorly directed. The reservoir is situated anteriorly in the right side of the cell and the nucleus is near the midline of the left side. The cells move by gliding with the flagellum.