Pinctada is a genus of saltwater clams, marine bivalve molluscs in the family Pteriidae, the pearl oysters. These oysters have a strong inner shell layer composed of nacre, also known as "mother of pearl".Pearl oysters are not closely related to either the edible oysters of family Ostreidae, or the freshwater pearl mussels of the families Unionidae and Margaritiferidae.Pinctada maxima pearl oysters are the only oyster species that produces South Sea pearls.