The present book is the result of decades of investigation of the European Clausiliidae. The focus points of this investigation were taxonomy and phylogeny of the different groups; the respective work is based on shell and genital morphology and DNA studies. For the species concept used for taxonomic work informative characters delimiting species taxa are decisive. The frequencies of dextrality and of interspecies hybridization in European Clausiliidae and the resulting problems for species delimitation are discussed. As result of these studies a species list of the European Clausiliidae is proposed. Based on morphological, molecular, paleontological and ecological work an attempt is made to reconstruct the evolutionary history of the European Clausiliidae. In addition their diversity in space and time is described by a comparative list of rich clausiliid faunas in Europe, extant and fossil.