Bythinella darrieuxii (de Folin & Bérillon, 1877)
Original taxon: Paludinella darrieuxii.
The shell is characterized by a double keel from the second whorl onward: the first one below the adapical suture, and the second one, less marked, on abapical position. This is the reason why the aperture looks somewhat quadrilateral, but with a rounded base. The columellar margin, slightly reflected, covers the umbilicus, which is reduced, in adult specimens, to an extremely thin slit.
A specimen from the metallic pipe situated at about 300m, north of the church of Arnéguy. 2,4mm. Altitude ≈ 270m.
