Agnatha: a group of primitive jawless vertebrates that includes the lampreys, hagfishes, and many fossil fishlike forms.
Chondrichthyes: a class of fishes that includes those with a cartilaginous skeleton.
External Anatomy: relating to the outside or outer bodily structures found on an organism
Fish: any of various cold-blooded, aquatic vertebrates, having gills, commonly fins, and typically an elongated body covered with scales
Gills: the paired respiratory organ of fishes and some amphibians, by which oxygen is extracted from water flowing over surfaces within or attached to the walls of the pharynx.
Invertebrate: not vertebrate; without a backbone.
Operculum: the bony flap of skin over the gills that protects the gills and helps the fish breath when it is not swimming
Osteichthyes: a class of fishes that includes those with a bony skeleton.
Species: a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.
Swim Bladder: gas-filled sac that helps keep fish buoyant
Taxonomic Class: a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank that fits between phylum and order.
Vertebrate: having vertebrae; having a backbone or spinal column