Granite mushroom stones, or wave stones, are limestone boulders undercut by water. These take the form of solitary sentinels of limestone which still bear the unmistakable marks of long-continued erosion by lapping waves at the edge of lakes which have since vanished or retreated. These stone sentinels are sometimes shaped like granite mushroom stones; others have an overhang facing in just one direction, but all are notched and undercut in such a fashion as to suggest prolonged exposure to standing water at some time in the past. The mushroom-shaped stones are produced where the notching forms a fairly even circle around the stone.