Green Sea Urchin (Lytechinus semituberdulatus), Galapagos Islands, Ecuador

Here's a cool shell found in the Galapagos Islands of Ecuador. It's the shell of an endemic, or locally found, green sea urchin ( Lytechinus semituberculatus ), I think, because of the green coloring. The coloring could be caused by other reasons, I guess. We saw the living green sea urchins below water, too.