cartilaginous fishes
Fish with skeletons made of cartilage rather than bones; their flesh usually contains no bones.
sturgeon 
This freshwater or saltwater fish of imposing size is prized for its firm flesh and its eggs, which constitute the true caviar.
skate 
Its pinkish or whitish boneless flesh must be cooked until it is no longer viscous or gelatinous; the main edible parts are the wings (pectoral fins).
smooth hound 
Shark of the Mediterranean, Atlantic and Pacific; its white flesh has a faint smell of ammonia that disappears with cooking.
larger spotted dogfish 
Shark of the Mediterranean and Atlantic; it tastes best if cooked when very fresh and served with a flavorful sauce.