The present classification of the New Zealand Onchidiidae into six species is shown to be incorrect. Three of the species,Onchidella patelloides(Quoy and Gaimard),O. irrorata(Gould),O. obscura(Plate), have insufficient differences for separation. They are reclassified under the species nameOnchidella nigricans(Quoy and Gaimard). BothO. flavescens(Wissel) andO. campbelli(Filhol) possess sufficient distinctive features for classification as species.