See text Onchidiidae are a family of small, air-breathing sea (and land) slugs.

In the late 1920s Hoffmann revised the family (based on the descriptions), and classified the described species into genera.

[4] Labbé also made mistakes in describing the anatomy of some species,[5] and the Onchidiidae was not revised again for over 80 years.

The genus Onchidium was revised in 2016 based on natural history, comparative anatomy, and DNA sequences.

The marine ones breathe and move around and feed during low tide, when the water recedes and the slugs are exposed to the air.