Pecten scallop shell (Pecten sp.), resting on a piece of coral. This scallop is a bivalve mollusc, its two shells (red) connected together by a hinge at the bottom. The shells, made of minerals containing calcium, are ridged and interlock with each other along their edges. The hinged shells are opened and closed by a single muscle. Scallops can swim through the water by rapidly opening and closing their shells. Magnification: x1.5 when printed 10 centimetres tall.