Tuns

Family Tonnidae. Tun shells are usually thinner and roomier than helmet shells.

They are almost exclusively tropical, prefer deeper water, and feed mainly on fish,

sea urchins and crustaceans. Their free swimming larval life is lengthy and has helped

some species to spread great distances.

Chambered Nautilus

Family Spirulidae. Small, attractive coiled white shells, resembling ram's horns, found on

many tropical beaches, are the internal brace for a small deep sea squid, the Spirula.

Each of its tiny, pearly chambers contains gas. When the squid dies and its flesh rots, the

shell floats to the surface of the ocean and is washed ashore.