(a) : Aristotle's lantern occurs in the Class Echinoidea. Five teeth surrounding the mouth are attached to a masticatory apparatus, called Aristotle's lantern, after its discoverer and because of its resemblance to an ancient Greek ship-lantern. It is situated within the test and projects slightly through the mouth. It consists of five large calcareous plates, called pyramids or alveoli. By means of special protractor and retractor muscles the lantern can be partially protracted and retracted through the mouth. Aristotle's lantern is used in feeding.