Most animals have hard parts, or skeletons, that they use for protection and for the attachment of muscles. These two objects are the hard parts of two very different marine organisms.
The colourful shell is from an abalone, an edible sea snail, otherwise known as ear-shells, sea ears, muttonfish, venus's-ears, paua, or, in Great Britain, ormers. The holes in the shell are vents out of which sea-water is forced after flowing over the gills during breathing.
The duller, yet beautifully sculptured structure sitting in the ormer shell is a sea potato. Sometimes called heart urchins, and known scientifically as Echinocardium cordatum, sea potatoes live in offshore burrows in the sand. They are relatives of sea urchins and star fish.