Echinocardium cordatum Pennant, 1777
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.
Echinodermata (Phylum) > Echinozoa (Subphylum) > Echinoidea (Class) > Euechinoidea (Subclass) > Spatangoida (Order) > Loveniidae
(Family) > Echinocardium
(Genus) > cordatum (Species)
Widespread 3-300 metres, around New Zealand and Australia, north and south Pacific, the Atlantic, and Mediterranean, but discontinuously. Not found in tropical seas