(Triakis semifasciata), small shark of the family Triakidae found in shallow water along the Pacific coast of the United States. A slim, narrow-headed shark with small, three-cusped teeth, it grows about 90 to 150 centimetres (3 to 5 feet) long. It is gray, distinctively marked with transverse black bars on its back and black spots on its sides. It preys on fishes and crustaceans. Though often considered harmless to man, it may bite.