Description of Arcella hemisphaerica:
Testate amoeba, organic test, with lobose pseudopodia emerging from central basal aperture. The shell is yellow or brown, circular and hemispherical in lateral view. The test surface is either smooth or irregular and has small pores. The aperture is slightly invaginated, circular and bordered by a lip. Diameter of shell 45-63 microns, depth 23-42 microns and diameter of aperture 11-18 microns.