Archerella flavum (Archer, 1877) Loeblich and Tappan, 1961

Diagnose: Test ovoid or elongated elliptical, with parallel sides, symmetrical, more or less compressed; composed of a transparent rigid organic membrane, without xenosomes; test brown or yellowish; two apertures at opposite poles; aperture elliptical; nucleus central; one to several contractile vacuoles; straight filopodia, sparsely branched, radiating. Zoochlorellae present.

Dimensions: Length 45-77 µm.

Ecology: in wet or submerged Sphagnum vegetation.

Remarks: Within a population the shape of the test can be very different, from elliptical to sigar-shaped. This genus is together with genus Amphitrema closely related to the Labyrinthulidae. It has been transferred to the Stramenopiles by Gomaa et al (2013).