Cone shells - leopard cone snail (Lithoconus leopardus) and marbled cone snail (Conus marmoreus). These are shells of predatory, venomous sea snails.
A Scallop seashell. Scallops are saltwater clams or bivalves in the family Pectinidae. The elegant fan shape is an iconic image of marine life.
The shell of the European edible sea urchin (Echinus esculentus), family Echinoidea. Sea urchins move slowly, feeding primarily on algae.