Over het vroegere voorkomen van de rivierparelmossel Margaritifera auricularia in Nederland

On the former occurrence of the river pearl mussel Margaritifera auricularia in The Netherlands Two shell fragments of Margaritifera auricularia have been found in deposits of the river Rhine at Valkenburg (province of Zuid-Holland). These deposits were sampled during an excavation of a Roman settlement; the shells are about 1900 years old. In the light of these new data the old records of ‘ ‘Unio margaritifera’ have been reconsidered. It was thought that the 19th century records were due to misidentification because a suitable environment was not present in The Netherlands; also there is no material available in collections. The Valkenburg material now draws attention to the possibility that the old records refer to M. auricularia rather than M. margaritifera or a species of Unio.