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Genus Centropyxis

Shell is circular, irregular circular of ovoid in apertural (or dorsal) view, flattened in the area of the aperture in lateral view. Aperture is located on ventral side, invaginated, eccentric, circular to ovate. The shell is colorless to brown and may or may not be covered by agglutinating material, which varies from mineral grains to organic debris, particularly diatom frustules. Shell may or may not be ornamented with spines of varying number and length. Ecology: freshwater, moss. Type species: Centropyxis aculeata (Ehrenberg, 1838) Stein, 1857