Lampreys are eel-like, scaleless animals. They range from about 15 to 100 centimetres (6 to 40 inches) long. They have well-developed eyes, one or two dorsal fins, a tail fin, a single nostril on top of the head, and seven gill openings on each side of the body. Like the hagfish, they lack bones, jaws, and paired fins. The skeleton of a lamprey consists of cartilage; the mouth is a round, sucking hole with horny teeth.