Morphological heterogeneity of the pinnotherid genera Durckheimia and Xanthasia has long been recognised. In particular, the segmentation of the third maxilliped palp, whether 2- or 3-segmented, is presently regarded as a conservative and useful generic trait. Durckheimia and Xanthasia, however, both contain species with both types of third maxilliped palps. Prior to the present study, five species were placed in Durckheimia, four bearing a 3-segmented palp and one, D. besutensis, with a 2-segmented palp. Durckheimia is restricted to three species, D. carinipes (type species), D. caeca, and D. lochi. Durckheimia yokotai is synonymised with D. caeca. The aberrant D. besutensis is transferred to a new genus, Serenotheres. Xanthasia is restricted to its type species, X. murigera, which bears a 2-segmented palp. Xanthasia whitei, with a 3-segmented third maxilliped palp and only superficially resembling X. murigera, is made the type of a new genus, Tridacnotheres. All species are illustrated and diagnosed, and a key to the species of Durckheimia is presented.