The shell of the European edible sea urchin (Echinus esculentus), family Echinoidea. Sea urchins move slowly, feeding primarily on algae.
A Schilder's Tiger cowrie sea shell (Cyprae tigris f, shilderiana). These are large sea snails, marine gastropod molluscs in the family Cypraeidae. The beautiful porcelain-like shells are often used in jewelry.
This spiral sea shell is of the family Architectonicidae. Known as the staircase shells or sundials, they are sea snails, marine gastropod mollusks.