
Cyclopyxis arenata (Cushman, 1930) Boltovskoy, 1956
Basionym: Pseudarcella arenata Cushman, 1930
Diagnosis. Cushman (1930): Shell about twice as broad as high, plano-convex in side view, dorsal side strongly convex, ventral side flattened and slightly concave in the middle, cicrcular in outline; wall very thin, composed of distinct sand grains firmly cemented, somewhat chitinous; aperture circulare with a simple flattened tooth.
Boltovskoy and Lena (1966): Hemispherical shell. Convex dorsal side, ventral somewhat concave in its middle part. Rounded aperture, located in the center of the ventral side. Agglutinated walls, covered with medium-sized sand grains. Color from white to ocher.
Dimensions: According to Cushman (1930): Shell diameter 250—300 µm; height 150—180 µm.
Habitat: Freshwater.
Geographical distribution: Rio Grande, Ushuaia, Patagonia (Boltovskoy and Lena (1966)
