Notes on the history of the malacological collection of the Nationaal Natuurhistorisch Museum, Leiden, The Netherlands, 1. The rediscovery of type-material of Bulla albocincta Van der Hoeven, 1839 (Mollusca: Gastropoda: Opisthobranchia: Hydatinidae)

A study on the history of malacological collections in the Netherlands, undertaken by one of the authors (AB), revealed that the whereabouts of type material of Bulla albocincta Van der Hoeven, 1839, were unknown. Two specimens, representing a syntype and a possible syntype, were discovered in the collections of the Nationaal Natuurhistorisch Museum, Leiden, The Netherlands. In this paper the history of the Dalen collection, from which the two specimens originated, is discussed. A lectotype of Bulla albocincta is designated. Furthermore, an English translation of the original diagnosis, which was published in Dutch, is given.