Phylum Chordata includes invertebrates as well as vertebrates.  The invertebrate chordates are the cephalochordates (Amphioxus) and tunicates.  This exercise includes them as well as the vertebrate chordate fishes.  The jawless fish are the lampreys and hagfish.  The jawed fish include the cartilaginous sharks and rays and the largest group of vertebrates, the bony fish.