A new genus and species of Hydrobiidae is described from north central Peloponnese peninsula, Greece: Tridentalia lykaia. Additionally a note on Achaiohydrobia Falniowski, 2021 is given: Achaiohydrobia moreana Hofman & Grego, 2021 is a junior synonym of Bythinella corrosa Glöer & Hirschfelder, 2020.
In this study, Truncatellina cylindrica (A. Férussac, 1807), Truncatellina rothi (Hesse, 1916), and Truncatellina haasi Venmans, 1957 were investigated, and a lectotype for Isthmia rothi was selected. So far, the three species have only been defined by their shell morphology. Intensified collection efforts throughout the past 100 years increased the number of specimens available, and it has become increasingly questionable whether these three species represent different taxa. In this study 1070 specimens were photographed, and measurements of several shell traits were taken. A multivariate ratio analysis revealed that the morphological trait variation of T. rothi (and probably T. haasi as well) is mainly covered by the variability of T. cylindrica. There is no morphological evidence that the investigated specimens represent different taxa. A genetic study is needed to reveal possible cryptic clades.
New data on the shell and the genital anatomy as well as on distribution and ecology of Eubrephulus peloponnesicus (E. Gittenberger, 1984) are presented. The morphology of genitalia and shell confirm the classification as Eubrephulus. Differences to the genera Chondrula and Mastus are discussed.