the class of fishes comprising the cartilaginous fishes, which includes the sharks.

"a class of vertebrates comprising the fishes with cartilaginous skeletons. The majority belong to the subclass Elasmobranchii (skates, rays, and sharks). Most cartilaginous fishes are marine carnivores with powerful jaws. Unlike bony fishes, they have no swim bladder, and therefore avoid sinking only by constant swimming with the aid of an asymmetrical tail. There is no operculum covering the gill slits, the first which is modified as a spiracle. Fertilization is internal for the few eggs produced are consequently yolky, large, and well-protected. Some cartilaginous fishes show vivaparous development of the young" (119).

Cartilaginous fish, having cartilage rather than bone within their bodies (sharks and rays).