Pecten jacobaeus "PLAIN" (aka Santiago de Compostela shell) called pendant on rope.

Pecten jacobaeus, the Mediterranean scallop, is a species of scallop, an edible saltwater clam, a marine bivalve mollusc in the family Pectinidae, the scallops Pecten jacobaeus can reach a length of about 120–140 millimetres (4.7–5.5 in). The two valves have different shapes. The lower valve, with which the animal rests on the bottom, is very convex and light-colored, while the upper valve is flat and brown. They show 14 to 16 ribs (radial wrinkles) with a more or less rectangular cross section. The inside of the valves is porcelain-like smooth. The mollusc has at the edge of the mantle many short tentacles, between which there are a total of 60 blue-millimeter lens eyes. By quickly closing of the two valves it can swim away several meters in case of danger. These scallops eat planktonic organisms and other floating food particles, which they obtain by filtering sea water with their gills. In a Christian context, this species is considered to be the scallop which is traditionally associated with Saint James, also known as James, son of Zebedee, also known as Saint Jacob, hence the specific name jacobaeus. It is also known as the "Pilgrim's scallop", as the shells were used by the pilgrims in the Middle Ages as a cup