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Genus Trigonopyxis

Shell is circular in frontal view, hemispherical or higher in lateral view; yellowish or brownish. Dorsal face is covered by xenosomes, ventral face is smooth. Aperture is invaginated, frequently triangular but more often irregular, always surrounded by a ring of organic cement, with a second membranous wall. Ecology: soil, litter, moss. Type species: Trigonopyxis arcula (Leidy, 1879)