The establishment of epitypes (together with the emended diagnoses) for three species of Euglenaria Karnkowska, E. W. Linton et Kwiatowski [Eu. anabaena (Mainx) Karnkowska et E. W. Linton; Eu. caudata (Hübner) Karnkowska et E. W. Linton; and Eu. clavata (Skuja) Karnkowska et E. W. Linton] and two species of Euglena Ehrenberg [E. granulata (Klebs) Schmitz and E. velata Klebs] was achieved due to literature studies, verification of morphological diagnostic features (cell size, cell shape, number of chloroplasts, the presence of mucocysts), as well as molecular characters (SSU rDNA). Now all these species are easy to identify and distinguish, despite their high morphological similarity, that is, spindle-shaped (or cylindrically spindle-shaped) cells and parietal, lobed chloroplasts with a single pyrenoid, accompanied by bilateral paramylon caps located on both sides of the chloroplast. E. granulata is the only species in this group that has spherical mucocysts. E. velata is distinguished by the largest cells (90–150 μm) and has the highest number of chloroplasts (>30). Eu. anabaena has the fewest chloroplasts (usually 3–6), and its cells are always (whether the organism is swimming or not) spindle-shaped or cylindrically spindle-shaped, in contrast to the cells of Eu. clavata, which are club-shaped (clavate) while swimming and only after stopping change to resemble the shape of a spindle or a cylindrical spindle; Eu. clavata has numerous chloroplasts (15–20). Eu. caudata is characterized by asymmetrical spindle-shaped (fusiform) cells, that is, with an elongated rear section and a shorter front section; the number of chloroplasts normally ranges from 7 to 15.