Re-discovery of the type series of the Indian freshwater mussel <i>Parreysia corrugata</i> (O. F. Müller, 1774) with the designation of the lectotype (Bivalvia: Unionidae: Parreysiinae)

India represents a tropical biodiversity hotspot, harbouring a unique and largely endemic fauna of freshwater mussels (Bivalvia: Unionidae). Unfortunately, the type series of many freshwater mussel taxa historically described from this country are thought to be lost. Here, we report on the rediscovery of the type series of <i>Parreysia corrugata</i> (O.F Müller, 1774) (Parreysiinae: Parreysiini) in the Natural History Museum of Denmark (NHMD), Copenhagen. It contains four syntypes (complete shells), which were examined by means of morphological and geometric morphometric techniques. We show that the nominal taxon <i>Parreysia corrugata</i> was established based on a composite type series, because one of the syntypes belongs to another species, <i>Potomida semirugata</i> (Lamarck, 1819) (Gonideinae: Lamprotulini), originating from the Middle East. To fix the taxonomic identity of the Indian species, a syntype (lot NHMD 916309) that was most likely illustrated by O.F. Müller in 1779 is designated here as the lectotype of <i>Parreysia corrugata</i>. The lectotype, paralectotypes and corresponding labels are illustrated in detail. Our new findings clarify the taxonomic concept of <i>Parreysia corrugata</i> and contribute to the further development of the Indian Unionidae taxonomy. http://www.zoobank.org/urn:lsid:zoobank.org:pub:AD4E3637-66BC-4C48-BCC6-2E910451CB89