Rectificatie en aanvulling betreffende het voorkomen van Noord-Amerikaanse aquatische mollusken in het binnenwater van West-Europa

A malfunction during the electronic dispatch of Table 1 in Mienis (2001) resulted in the shift of two symbols to the wrong column. Therefore a correction of Table 1 is given. A recent publication by Renker & Kobialka (2001) concerning the increasing presence of Gyraulus parvus in northwestern Germany raises the question why this species has never been encountered in the Netherlands.