Wikipedia
Peronia
Not to be confused with the plant genus, also named Peronia, a taxonomic synonym of Thalia
Peronia is a genus of air-breathing sea slugs, a shell-less marine pulmonate gastropod mollusks in the family Onchidiidae.
Even if the name Onchis Férussac, 1821 is older than Peronia Fleming, 1822, there is no need to replace Peronia (adopted by Labbé and others) by Onchis (a name that was almost completely forgotten). The systematics of the family Onchidiidae is already quite confusing and there is no need to disrupt it further. Therefore Onchis is accepted as a synonym of Peronia.