Aantekeningen over de Bithyniidae (Gastropoda, Streptoneura) in het Nederlandse Kwartair

The following species and forms of the gastropod family Bithyniidae, from Quaternary deposits of the Netherlands, could be identified. Neumayria crassitesta (Bromine, 1885), occurring in sediments of Holsteinian, Waalian and Tiglian age. Bithynia tentaculata (Linne, 1758), found in Holocene, Weichselian, Eemian, Holsteinian and Tiglian deposits. Bithynia tentaculata (Linne, 1758) subsp. has been encountered in sediments of Waalian age in a clay-pit near Bavel in the municipality of Breda (province of Noord Brabant). It differs from the typical species by its reflected peristome. The systematical position of this subspecies is not yet established. In this connection the genus Pseudemmericia Schlickum, 1968 is discussed. The present author does not want to express his opinion on the question whether this genus has rightly or wrongly been introduced. Bithynia leachi (Sheppard, 1823) is known from sediments with an age of Holocene, Weichselian, Waalian and Tiglian. Bithynia leachi (Sheppard, 1823) forma troscheli (Paasch, 1842) is known from Holsteinian, Waalian, Tiglian and “younger Pleistocene” deposits. Furthermore, this investigation also allows the following conclusions: – Opercula of Lithoglyphus naticoides (C. Pfeiffer, 1828), regularly mentioned in the Dutch literature, turned out te belong to Neumayria crassitesta. Opercula of L. naticoides have never been found in the fossil record. – Records of Bithynia tentaculata in Dutch literature should be distrusted with respect to their correct identification. They might also belong to B. leachi N. crassitesta, forma troscheli or to B. tentaculata subsp.