The Gumboot Chiton (Cryptochiton stelleri) is the largest chiton in the world and can grow up to 13" long. It resembles a football in size, shape, color and texture. It doesn't appear to have the signature eight articulated plates of a chiton, but upon closer examination of the photo below, you can distinguish the outline of the plates under the leathery "girdle" that has completely overgrown them.
We have found Gumboot chitons in many locations, but they seem to be more plentiful in areas where there is an abundance of kelp. Gumboot Chitons graze on algae, have few enemies, and can live for more than twenty years.
The Gumboot I'm holding in the photo below has folded itself in half, on its way to curling into a ball. This defense mechanism of curling its body to protect its vulnerable underside from predators, is used by all chitons and has earned them the nickname "sea cradles".
Never pry a Gumboot Chiton off a rock, as you could damage its foot, but if you find one that is not attached, turn it over for closer observation. The foot is the oval shape in the middle (see photo below) and there are gills along each side of the foot (in the photo, the gills are hidden in the narrow opening on either side of the foot).