Cuttle fish (cuttlefish, Sepia spp.) belong to the class Cephalopoda, phylum Mollusca. They are intelligent, soft-bodied animals with a unique internal shell (cuttlebone), eight arms, and two tentacles. Flat fish (e.g. sole, flounder) and silver fish are vertebrates (Chordata); star fish (sea stars) are Echinoderms. Other molluscs include snails, clams, squid, and octopus.