Distribución del género neotropical Potamolithus Pilsbry y Rush, 1896 (Gastropoda: Hydrobiidae) en el estuario del Río de la Plata

The distribution patterns of several species of the genus Potamolithus from the Río de la Plata estuary was analysed. Nineteen localities were sampled and five malacological museum collections were studied. Species found were: Potamolithus agapetus Pilsbry, 1911, P. buschii (Frauenfeld, 1865), P. conicus (Brot, 1867), P. lapidum (d’Orbigny, 1835), P. orbignyi Pilsbry, 1896 y P. petitianus (d’Orbigny, 1840). P. filipponei von Ihering, 1910 was not found in Montevideo (R. O. Uruguay), its type locality. Relationships between different kind of substrates, salinity gradient and the distribution of Potamolithus spp. in the littoral were established as follows: Potamolithus spp. inhabit in the Río de la Plata estuary, over hard substrate (rocks, artificial substrate and compacted sandy silt) and salinity is a limiting factor on the distribution of these species