Two new species of Tryonia (Caenogastropoda: Cochliopidae) from the late Pleistocene of Coahuila, northern Mexico

摘要

Two new species of Pleistocene freshwater snails of the genus Tryonia Stimpson (1865) from Coahuila, northern Mexico, are described. One of them, Tryonia hershleri new species, belongs to a group of species that have shells with characteristic prominent axial ribs. The second species, Tryonia pseudocircumstriata new species, is similar to recent and fossil species from the Pecos River in the southwestern United States. Contrary to earlier practice, we propose to use different species names for Pleistocene and extant Tryonia from the Pecos River.