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.