Petalomonas Stein, 1859 (ref. ID; 4656, 4950) or 1878 (ref. ID; 4921, 6733) reported year? (ref. ID; 1618)
Order Euglenida Butschli, 1884 (ref. ID; 4872)
Order Euglenophyceae Schoenichen, 1925 (ref. ID; 4907)
Euglenozoa Cavalier-Smith, 1981: Euglenophyceae Schoenichen, 1925 (= Euglenida Butschli, 1884) (ref. ID; 5772)

[ref. ID; 1618]
Oval or pyriform; not plastic; pellicle often with straight or spiral furrows; a single flagellum; paramylum bodies; a nucleus; holozoic or saprozoic. Many species in fresh water and a few in salt water. (ref. ID; 1618)

Petalomonas abscissa (Dujardin, 1841) Stein, 1859 (ref. ID; 4872) reported year? (ref. ID; 3517, 4950)
Syn; Cyclidium abscissum Dujardin (ref. ID; 4950)
Description; Emarginate posterior end. With two ridges running along dorsal surface of cell and with one narrow curved groove ventrally, the ventral groove with strengthened margins - forming a double keel. Lateral edges of cell with ridges. The two dorsal ridges set off a raised central section. The dorsal keel also decreases in height toward the posterior part of the cell. One flagellum 1+1/2-2 times cell length, pointing anteriorly. Flagellar pocket to the left ventral side. Cells gliding. (ref. ID; 4872)
Remarks; The original description of P. abscissa is relatively broad and the cell form varies from roundish to triangular is shape. We apply the identity developed by Larsen (1987) and by Larsen & Patterson (1990), relying on the outline and the characteristic ventral double keel. We note that there are minor differences in the location of the ridges and keel. The size of P. abscissa is less than that reported elsewhere: 27.5-28 um (Lemmermann 1914; Skuja 1948; Huber-Pestalozzi 1955), 20-25 um (Larsen 1987) and 17 um (Larsen & Patterson 1990). (ref. ID; 4872)
Measurements; Cell length 14 um, range 10-16 um. (ref. ID; 4872)
Petalomonas mediocanellata Stein, 1878 (ref. ID; 4656) reported year? (ref. ID; 1618, 3517, 4950)
Description; Ovoid with longitudinal furrows on two sides; flagellum about as long as the body. (ref. ID; 1618)
Measurements; 21-26 um long. (ref. ID; 1618)
Petalomonas pusilla Skuja, 1948 (ref. ID; 4656, 4907, 4921) reported year? (ref. ID; 3517, 4950)
Syn; Petalomonas poosilla Larsen & Patterson, 1990 (ref. ID; 4921)
Description; Cell 5-6 um long, flattened with ovate outline, no visible surface structures. One single rather thick flagellum emerges from a flagellar pocket. The part of flagellum located outside pocket slightly shorter than cell. Contractile vacuole empties into flagellar pocket. Nucleus located posterior. Usually moves with a smooth gliding with flagellum directed forwards, only distal half of emerging flagellum beats, proximal part usually held stiff. For short periods, when cell changes direction, flagellum may trail behind cell. (ref. ID; 4907)
Comments; The combination of small size and the lack of surface structures precludes confusion with other englenids. (ref. ID; 4907)