"Opistobranquios" (Mollusca: Gastropoda) de la colección malacológica Lluís Dantart

“Opistobranchs” (Mollusca: Gastropoda) from the Lluís Dantart malacological collection.—The “opisthobranchs” from the Lluís Dantart collection, deposited at the Animal Biodiversity Resource Center (CRBA) of the Universitat de Barcelona, are studied. The studied samples belong to the orders Acteonacea, Ringiculida, Pleurobranchomorpha, Nudibranchia, Cephalaspidea, Anaspidea, Thecosomata, Umbraculida and Sacoglossa. For each lot, its taxonomic identification has been verified (correcting it when it was considered erroneous), and its nomenclature has been adapted to current knowledge. In total, 1,095 specimens have been studied, belonging to 68 different species and totaling 265 records. The specimens mostly belong to samples collected on the Catalan coasts, but also from different points in the Iberian Peninsula, the Balearic Islands, and the Bissagos Archipelago (off the coast of Guinea-Bissau, in West Africa). Of the 68 species, 2 belong to Acteonacea, 3 to Ringiculida, 17 to Nudibranchia, 3 to Pleurobranchomorpha, 1 to Umbraculida, 1 to Anaspidea, 31 to Cephalaspidea, 9 to Thecosomata and 1 to Sacoglossa. For each of the studied species, all the data of their records in the collection are provided: locality, date of collection, number of specimens, whether they are dry (shells) or preserved in alcohol, depth at which the specimen was found and, occasionally, some details of the substrate, as well as the sample collector. For some of the species, interesting taxonomic or biogeographic observations are added. Of all the studied species, Retusa robagliana and Atys brocchii had not been previously reported from the Catalan coasts; the latter and Ringicula buccinea were neither included in the most recent species catalogs of opisthobranchs or mollusks in general for the Iberian Peninsula. The nudibranch Knoutsodonta pictoni is reported for the first time after its original description and therefore represents the first record of the species for Catalan waters and for those of the Iberian Peninsula. The importance of natural history collections present in museums or research centers for the scientific knowledge of biodiversity and its formative aspect for the general public is highlighted