Seashells come in a vast array of shapes, colors, and sizes, but they all have one basic thing in common: They're the partial remains of dead animals. There are literally hundreds of thousands of animal species that grow and leave behind seashells, ranging in size from microscopic to sofa size.
Most of what we think of as classic seashells were made by marine mollusks. That's because they make the sturdiest, longest-lasting shells. Apart from mollusk shells, other shells that can be found on beaches are those of barnacles, horseshoe crabs and brachiopods.
