The Narwal, or Unicorn-fish, attains a length of from twenty to twenty-five feet. He is of a grey-white colour, punctured with many white spots, and as his head is not disproportionate to the length of his body, may rank among the handsomest cetaceans. He distinguishes himself, as is well known, from all other members of the family by the long twisted tooth or horn projecting horizontally from the upper jaw. This mighty weapon, the true use of which has not yet been fully ascertained, was formerly sold at a very high price, as proceeding from the fabulous unicorn; at present, it is only paid according to the worth of its excellent ivory, which is harder, heavier, and less liable to turn yellow than that of the elephant. The whalers are therefore highly delighted when they can pick up a chance narwal, but this only succeeds in narrow bays; for the unicorn-fish is an excellent swimmer, and extremely watchful. In spite of his menacing appearance, he is a harmless sociable creature, fond of gambolling and crossing swords playfully with his compeers. It is remarkable that the opening of the mouth of so huge an animal is scarcely large enough to admit the hand of a man. Scoresby found in the stomach of a narwal remains of cuttle fishes, which seem to form his chief aliment, besides pieces of skates and plaice. The narwal is frequent about Davis' Straits and Disco Bay, but is nowhere found in the Pacific, having most likely not yet discovered the north-western passage. He rarely wanders into the temperate seas, yet one was caught, in 1800, near Boston in Lincolnshire, and two others, in 1736, on the German coast of the North Sea. The Dolphin tribe is distinguished from the cachalot by a more proportionate head; from the narwal by the absence of the long horn; and generally possesses sharp teeth in both jaws, all of one form. The number of species is very great; Linnæus distinguished four sperm-whales and three dolphins; now many naturalists acknowledge but one species of the former, while the dolphins have increased to more than thirty, and many are as yet unknown. [Illustration: Delphinus Delphis.] The most famous member of this numerous family is undoubtedly the classical Dolphin of the ancients (_Delphinus delphis_) which attains a length of from nine to ten feet, and is, according to Pliny, the swiftest of all animals, so as to merit the appellation of the "arrow of the sea." His lively troops often accompany for days the track of a ship, and agreeably interrupt the monotony of a long sea-voyage. As if in mockery of the most rapid sailer, they shoot past so as to vanish from the eye, and then return again with the same lightning-like velocity. Their spirits are so brisk that they frequently leap into the air, as if longing to expatiate in a lighter fluid. Hence, dolphins are the favourites of the mariner and the poet, who have vied in embellishing their history with the charms of fiction.