This species feeds on corals and other organisms. The endemic green sea urchin, Lytechinus semituberculatus , is also common. Sand dollars and sea biscuits are also echinoderms. Mollusks Mollusks are soft-bodied animals, most of which have some type of shell. Chitons are a primitive type of mollusk whose carapace consists usually of eight angled plates which overlap like shingles to form an effective armor.
Chitons are common in the intertidal zone.
They feed by rasping off microscopic algae from the rocks. Bivalves , or pelecypods, are a familiar and abundant group that includes the clams, cockles, mussels, oysters, and scallops. Most species filter feed on microscopic plant life. The Sally lightfoot , or red lava crab, Grapsus grapsus , is so abundant and so brightly colored with red above and blue below that no visitor could miss them. Their name comes from their habit of skipping across short stretches of water.