There are about 160 species of ACANTHOCHITONIDAE, divided in 2 subfamilies and with 12 genera, of which Acanthochitona (80 species in 2020) and Notoplax (41 species in 2020) are the most important ones.
Most Acanthochitons live in the shallows, under and on hard substrates. They are characterised by the valves which are usually sunken in the girdle. the girdle itselves has tufts of bristles set in regular rows on each side of the valves.
To get well prepared Acanthochitons is a challenge: the animals are difficult to preserve, but when well done they may be beautiful. They are always a curiosity.
For a list of genera and species:
http://www.marinespecies.org/aphia.php?p=taxdetails&id=91