The northern moon snail, scientific name Euspira heros (previously known by the scientific name Lunatia heros), is a species of large sea snail, a predatory marine gastropod mollusk in the family Naticidae, the moon snails (U.S.) or necklace snails (U.K.). This large snail is rather uncommon intertidally, but is much more common subtidally. This species, like all moon snails, feeds voraciously on clams and other snails.