All mollusks build their own shells, whether they live in water or on land. Creatures like snails, clams, oysters and mussels use an organ called a mantle to secrete layers of calcium carbonate, which ...

Variation in land-snail shell form has been extensively documented, but its causes are poorly understood. For no character are there general rules relating shell form to environmental characteristics, ...

Sea butterflies flit through the ocean on gossamer wings, each species with a style of its own. These tiny marine snails, or thecosomes, migrate up to surface waters at night to feed and sink to ...