Clypeaster tumidus (Tenison-Woods, 1878)
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) > Clypeasteroida (Order) > Clypaeasteridae
(Family) > Clypeaster
(Genus) > tumidus (Species)
Off north-east NZ, also Norfolk, Lord Howe Island and Australia
Marine, Lives from about 20-180 metres