Photograph of the lantern of <i>Paracentrotus lividus</i>.

<p>The view is from the side and slightly above the lantern. Two of the five segments of the lantern (la) are visible. The compasses (co) are partly elevated due to contraction of the compass elevator muscles (ce). Asterisks, compass depressors; pg, perignathic girdle (edge of test); t, tooth.