Oncis

Oncis is a genus of air-breathing sea slugs, a shell-less marine pulmonate gastropod mollusks in the family Onchidiidae.

The name of this genus has gone through a lot of tribulations. It was originally named Onchis by Férussac in 1821. In 1822 Fleming named Peronia with the same type species. In 1847 Herrmannsen renamed Onchis Férussac as Oncis for unjustified reasons. In 1893 Plate created the new name Oncis not Herrmanssen. And in 1938 Baker replaced the name Oncis Plate, 1893 by Platevindex Baker, 1938 (with type species Platevindex coriaceum Semper, 1885). However, Oncis Plate, 1893, is an available and potentially valid name, and Platevindex is an unnecessary replacement name as "Oncis" was not treated by Herrmannsen (1847) as the valid name of a taxon (ICZN Chapter 11 article 50.5)