(pet-al-owe-moan-ass), rigid heterotrophic (no plastids) euglenid, one emerging flagellum which points in front of the moving cells. The flagellum starts within the flagellar pocket (also called the reservoir) extends through a flagellar canal and out at or near the apex of the cell. Either absorbs soluble food or consumes small particles although no mouth is visible by light microscopy. Most species have longitudinal or slightly spiral ridges or folds. Mode of feeding is not clear. Common in freshwater and marine ecosystems. Differential interference contrast.