|Key Position: 2||Back to (1a)|
|2 a. Test circular in dorso-ventral view, plano-convex to hemispherical in lateral view, made of proteinaceous matter, surface smooth or punctate; aperture central, large and circular.
SEE Figure 2-1
|2 b. Test with or without spines, agglutinated with mineral grains, aperture sub-terminal or occasionally central, circular or oval, invaginated.|
Arcella vulgaris Ehrenberg 1830