The mouthparts of a sea urchin - called Aristotle's Lantern after the Greek philosopher who first described the structure in his Historia Animalium as looking like a lantern.
The Aristotle's Lantern is about 16 mm long.
Follow this link for a [video of these teeth in action](https://www.youtube.com/watch?v=IE26PTz7J0s).
Reference:
Historia Animalium (The History of Animals, Book IV), by Aristotle, translated by D'Arcy Wentworth Thompson, classics.mit.edu/Aristotle/history_anim.4.iv.html