Uncancylus concentricus (Mollusca, Gastropoda, Ancylidae): new occurrence in state of Rio de Janeiro, Brazil

The freshwater pateliform pulmonate snails considered as Ancylidae are represented in South America by seven genera according to Santos (2003): Anisancylus Pilsbry, 1924; Burnupia Walker, 1912; Ferrissia Walker, 1903; Gundlachia Pfeiffer, 1849; Hebetancylus Pilsbry, 1913; Laevapex Walker, 1903 and Uncancylus Pilsbry, 1913. The knowledge about occurrence, distribution and systematic of these snails is poorly known in Brazil, although fundamental to studies concerning biodiversity, not only by the continental dimensions of the country, but also considering the reduced number of malacologists.