For the first time, this book provides identification keys for all Dutch freshwater molluscs, including fossil Pleistocene species. In addition, maps on the basis of a 5 km square grid, give a picture of distribution and change of faunal composition. The book deals with 82 indigenous species, 4 non-indigenous species and 33 fossil species. Some species show a severe decline, such as Mercuria confusa, Myxas glutinosa, Omphiscola glabra, Unio crassus, while others are markedly expanding or even recent additions to the fauna, such as Corbicula fluminalis and C. fluminea.