Hog Island, a well-known oyster farm in Tomales Bay, north of San Francisco, raises the mollusks according to the classic French method and sells more than 3 million of them a year. The company, which also farms clams, runs this attractive oyster bar-retail shop in the busy Ferry Building. The U-shape granite counter seats about two dozen diners, who come here for oysters or clams on the half shell, clam chowder, rich oyster stew, oysters in beurre blanc, and steamed clams in beer. The small selection of wines complements the briny bivalves. You need to eat early, however, as the bar closes at 7:30.