Paraquadrula irregularis (Wallich, 1863)
Diagnosis: Shell transparent, broad oval, slightly compressed, composed of secreted quadratic or rectangular calcite plates in rows, sheet-like cement; nucleus vesicular.
Dimensions: Literature: 25-48 µm; my measurements: length 29-44 µm.
Ecology: fresh water and mosses; I found this species in a large deep lake, the Spiegelplas in The Netherlands, and in a sphagnum bog in Tirol, Austria. In 2014 I found a large number of specimens in dry mosses growing on the roof terrace of the Freie Universität Berlin. Hoogenraad & De Groot (1940) found this species in sediments of eutrophic calcite rich water.