Abstract
Three new species (Unionicola clarki, belli and smithae) are described for the first time and placed in a new subgenus, Anodontinatax. Related species, U. wolcotti (Piersig), U. mitchelli Conroy and U. intermedia (Koenike), are re-evaluated and also placed in this new subgenus. The subgenus Anodontinatax is intermediate in morphology between the subgenus Pentatax Thor (in Unionicola) and the genus Vietsatax Uchida and Imamura, and thus Vietsatax is reduced in rank to a subgenus in Unionicola.