Chambered Nautilus

Also called the Pearly Nautilus, Chambered Nautilus (Nautilus pompilius) dead shells wash ashore on open beaches in the Northern Territory of Australia after cyclones. The shell is secreted by a cephalopod and it is an ancient relative of octopuses and squid. When it washes ashore, the shell is covered by a whitish outer layer with a reddish brown pattern but once that layer is removed (by careful application of acid in this instance) the underlying pearly layer can be revealed. Internally, the nautilus shell represents a mathematical spiral.