The sconciglio is a murex sea snail, like the boccone. (The boccone made the famous royal purple dye for the ancients; the sconciglio provided blue or indigo dye). If you boil them long enough they're not bad: on pasta or a traditional zuppetta di sconcigli in southern Lazio.
As far as we know no one has ever put sconcigli on sconcigli, a provocative, twisty modern pasta shape.
Images by: graftedinelena, bravot