Fish

Abstract Fish (Subphylum Euchordata (vertebrata): Pisces) are sufficiently familiar to need little general introduction. It should be realized, however, that ‘Pisces’ does not represent a natural group but, corresponding to the word ‘fish’, embraces the jawless cyclostomes, the cartilaginous sharks and their allies (Chondrichthyes), and the bony fishes (Osteichthyes); each of these groupings constituting a separate and distinctive vertebrate class. Many of the technical terms refer primarily to bony fishes, but the names of fins and parts of the body apply equally to cartilaginous fishes.