Genus Cyphoderia Schlumberger, 1845
Diagnosis: shell more or less pyroid with a short cylindrical, curved neck, ovoid, usually round in cross-section, sometimes triangular or a little compressed; base round or tapered to mammillate tip; plates round or triangular, small, depending on species either adjoining or overlapping on organic matrix; filopodia long and thin; endoplasm with refractive grains; nucleus spherical, ovular.
Ecology: freshwater, aquatic mosses, sphagnum and detritus. In marshes and rivers.
Remarks: within a population most shells have a smooth hemispherical fundus. Some shells however have a more or less pronounced nipple-shaped apex. See my drawing above of a dividing specimen. One of the daughtercells has a mammilated apex. This shows that the presence or absence of such an apex is no argument to distinguish separate species, as Cyphoderia trochus and C. ampulla. This question was also discussed by Badewitz (2003).
Key to the species:
|1||Shell with a strongly curved dorsal part, resembling a croissant||Cyphoderia calceolus|
|–||Shell not croissant-shaped||2|
|2||Shell with distinct scales, shell usually > 100 µm||Cyphoderia ampulla|
|–||Shell apparently without scales, < 50 µm||Cyphoderia laevis|