Recovery of the Ernst and Eveline Marcus Mollusca Collection: an example of the challenges in the treatment of historical collections

Abstract An analytical inventory of the material studied by the eminent German zoologists Ernst and Eveline Marcus is presented, based on samples from their laboratory that were subsequently deposited in the Museum of Zoology, University of São Paulo. The collection consists of 1075 lots originating from 58 countries, comprising 3951 preserved specimens and 658 shells. It represents a total of 71 mollusc families (Gastropoda and Bivalvia), 185 genera, and 312 species, as well as 74 undetermined species identified at the genus level. Among this material, 58 primary type specimens of Gastropoda were identified. Additionally, 240 lots were recognized as voucher specimens from publications by the Marcuses. A curatorial process was undertaken, along with a search for complementary data. The primary objective is to provide the scientific community, particularly taxonomists, with a source of data derived from samples previously considered lost. A significant portion of the material retains scientific value, including confirmed or potential type specimens, although some originally alcohol-preserved specimens have been desiccated due to long-term storage conditions, and others lack labels or informative data. All samples have been registered, and their original or supplemented data are presented here in a concise, catalogue-like format, organized both systematically and alphabetically. Based on a review of the literature, Berghia benteva (Er. Marcus, 1958) is herein recognized as a valid species.