Answer:
Among the largest and most important invertebrate phyla are Porifera (sponges), Cnidaria (jellyfish, corals, and sea anemones), Platyhelminthes (flatworms), Nematoda (roundworms), Mollusca (snails, bivalves, squids, and octopuses), Annelida (segmented worms), Arthropoda (horseshoe crabs, spiders, crabs, centipedes, ..