Notes on the systematics, morphology and biostratigraphy of fossil holoplanktonic Mollusca, 12. On the identity of Hyalea perovalis Von Koenen, 1882 (Mollusca, Gastropoda, Euthecosomata) from the Early Miocene of the North Sea Basin

New specimens of the extremely rare cavoliniid pteropod ‘Hyalea perovalis’ Von Koenen, 1882, are recorded and illustrated from a boulder of Holsteiner Gestein (Early Miocene) collected at Nehmten, Schleswig-Holstein (Germany). Hyalea perovalis is here considered to be a junior synonym of Diacrolinia aquensis (Grateloup, 1827), which is known from the Early Burdigalian of the Aquitaine Basin, France. The occurrence of this species in the ‘Holsteiner Gestein’ substantiates previous correlations of the Late Vierlandian of the regional North Sea Basin stages with the Early Burdigalian of the international chronostratigraphic scheme.