a univalve

an aquatic shellfish (generally limited to mollusks with calcareous shells such as clams or snails, and excluding crustaceans such as shrimp or crabs)

color

an object that is thin and flat

counter for flat thin objects or sheets

beautiful

(archaic) beautiful

【counter word】measures (​flat, thin objects, e.g., postcards, sheets of paper, etc.)

Babylonia japonica: the Japanese babylon or Japanese ivory shell

shell / shellfish