Abstract
Six new species (Unionicola megachela, U. dobsoni, U. viviparaicola, U. hensleyi, U. causeyae and U. australindistincta) are described for the first time and placed in the subgenus Polyatax. These species are intermediate in character states between the subgenera Polyatax and Neoatax. The subgenus Neoatax is synonomized with Polyatax and abandoned. Ampullariatax new subgenus is erected for South and Central American taxa.