Uncommon in the Main Hawaiian Islands due to fishing but very common in the Northwestern Hawaiian Islands on shallow reefs where it feeds upon coralline algae.  Broadly oval with a blunt head, square tail, and smooth jaws.  Females purplish-brown with a white caudal peduncle and red fins, males blue with a darker saddle ahead of the eyes, fuchsia scale edges and overlay on the head, and a greenish-yellow blotch above the pectoral fin base.  Juveniles brown with three white stripes and white dots.  Attains 24 inches.  Endemic to Hawai'i.  Formerly known as Scarus perspicillatus.