Epopella plicata (Gray, 1843)
This is not a Mollusc. Other non-Molluscan Phyla (Echinodermata, Brachiopoda etc) have been included to help identify species that may be mistaken for Mollusca, but are not.
Arthropoda (Phylum) > Crustacea (Subphylum) > Hexanauplia (Class) > Thecostraca (Subclass) > Sessilia (Order) > Austrobalanidae
(Family) > Epopella
(Genus) > plicata (Species)
On mid-tidal rocks