<P> The mantle cavity is a central feature of molluscan biology . This cavity is formed by the mantle skirt, a double fold of mantle which encloses a water space . This space contains the mollusc's gills, anus, osphradium, nephridiopores, and gonopores . </P> <P> The mantle cavity functions as a respiratory chamber in most molluscs . In bivalves it is usually part of the feeding structure . In some molluscs the mantle cavity is a brood chamber, and in cephalopods and some bivalves such as scallops, it is a locomotory organ . </P> <P> The mantle is highly muscular . In cephalopods the contraction of the mantle is used to force water through a tubular siphon, the hyponome, and this propels the animal very rapidly through the water . In gastropods it is used as a kind of "foot" for locomotion over the surface . In Patella the foot includes the entire ventral surface of the animal . The foot of the Bivalvia is a fleshy process adapted by its form to digging rather than to locomotion . </P> <P> In shelled molluscs, the mantle is the organ that forms the shell, and adds to the shell to increase its size and strength as the animal grows . Shell material is secreted by the ectodermic (epithelial) cells of the mantle tissue . </P>

Where is the mantle located in the clam what is its function