1. Department of Botany and Zoology, Masaryk University, Kotlářská 2, CZ-611 37 Brno, Czech Republic.
2. Mollusca Group, Invertebrates Division, Department of Life Sciences, The Natural History Museum, London SW7 5BD, U.K.
3. Royal Belgian Institute of Natural Sciences, OD Taxonomy and Phylogeny, Vautierstraat 29, 1000 Brussels, Belgium.