Variation in radular teeth and acuspid side of the radula in Lacuna pallidula, L. parva and L. vincta (Gastropoda : Littorinidae) from the Isle of Wight, United Kingdom

The variation in the radula of three species of Lacuna has been investigate d and the back of the rachidian tooth is proposed as providing a new charac ter set of potentially high taxonomic value. The term basal plate is introd uced for the back of the rachidian tooth. Cusp and tooth morphology are clo sely related to diet and wear, and are subject to considerable homoplasy, w hereas the structure of the basal plate of the rachidian tooth provides a m ore neutral character set. The difference in this character set between the lacunids has been quantified using seven measurements and the exploratory multivariate statistical procedure principal component analysis. The basal plate of the rachidian tooth showed interspecific differences. The taxonomi c value of this new character set should be evaluated in further studies of other prosobranchs.