#NotesFromOurNaturalists SEASHELL FORMATION Most summer visitors take seashells for granted. Some folks don’t understand what seashells are. Seashells are made by animals called mollusks (snails, clams, oysters, scallops). Seashells fall into two categories: univalves and bivalves. Univalves or snails have one shell. Clams, scallops, and oysters are bivalves and have two shells. Mollusks hatch from eggs. Snails are born with a tiny shell. As they grow, they add to the shell. They thicken the she