Cephalothorax, 6 pairs of jointed appendages. Aquatic, but comes to shore to mate and lay eggs (spawn). Living fossil. Subphylum _ Class_ Many similar segments. Rounded body. Detritivore and decomposer. Two pairs of jointed legs per segments. Subphylum _ Class _ Deuterostome with 5 parts fused together. No arms. Spines. Elaborate jaws that eat kelp. Phylum _ Class _ Six legs with 4 scaly wings. Undergoes complete metamorphosis. Wings often large and showy. Pollinators. SUBPHYLUM _ ORDER _ Pentaradial symmetry. Arms with tube feet that have SUCKERS. Members of this class eat mussels. Phylum _ Class _ Two papery wings. Includes flies and mosquitos. ORDER_ First appendages are chelicerae, second are pedipalps. Terrestrial animals that include spiders and scorpions. Subphylum _ Class _ Almost entirely aquatic. Undergo ecdysiast. Jointed appendages. Includes Crab, lobsters, and pill bugs. Subphylum _ Class_ Solution 1. The organism here is the Horseshoe Crab. Subphylum: Chelicerata, Class: Merostomata 2. The organism here is millipede. Subphylum: Myriapoda, Class: Diplopoda 3. Sea urchins fit the description. Phylum: Echinodermata, Class: Echinoidea 4.The organism is butterfly. Subphylum: Hexapoda, Class: Insecta 5. Starfish is the organism. Phylum: Echinodermata, Class: Asteroidea 6. Order: Diptera 7. Subphylum: Chelicerata, Class: Arachnida 8. Subphylum: Crustacea, Class: Malacostraca.