Placunidae, also known as windowpane oysters, windowpane shells, and kapis shells, are a taxonomic family of saltwater clams, marine bivalve mollusks which are related to oysters and scallops. This family is best known for the shells of the species Placuna placenta, which are translucent, and are commonly used in shellcraft production. In some cultures, they were used as a form of light-admitting window.