megalith, megalithic structure
['hen-of-the-woods, hen of the woods, Polyporus frondosus, Grifola frondosa', 'chiton, coat-of-mail shell, sea cradle, polyplacophore', 'chain mail, ring mail, mail, chain armor, chain armour, ring armor, ring armour', 'ruddy turnstone, Arenaria interpres', 'buckeye, horse chestnut, conker', 'picket fence, paling', 'sea urchin']