NARWHAL, an animal of the order Cetacea (see MA__DIALIA, vol. xv. p. 398), belonging to the genus Monodon, of which there is but one species known, M. monoceros of Linnmus. It is included in the family Delphinidw or Dolphins, and closely resembles the Beluga or White Whale in all points of its structure except its dentition, which presents most anomalous characters. In the adult there are but two teeth present, both in the upper jaw. They lie horizontally side by side, and in the female they remain throughout life concealed in cavities of the bone, so that this sex is practically toothless. In the male the right tooth usually remains similarly concealed and abortive, but the left is immensely developed, attaining a length equal to more than half that of the entire animal. In a narwhal 12 feet long, from snout to end of tail, the exserted portion of the tusk may measure 6 or 7 and occasionally 8 feet in length. It projects horizontally forwards from the head in the form of a cylindrical or slightly tapering, pointed tusk, composed of ivory, with a central cavity reaching almost to the apex, without enamel, and with the surface marked by spira). grooves and ridges, running in a sinistral direction. Occasionally both left and right tusks are developed, in which case the direction of the grooves is not reversed, but the same in both. No instance has ever been met with of the complete development of the right tusk associated with a rudimentary condition of the left. In very young animals several small additional teeth, irregular in number and position, are present, but these usually disappear soon after birth.

The head is rather short and rounded; the fore limbs or paddles are small and broad compared with those of most dolphins; and (as in Beluga) the median dorsal fin, found in nearly all other members of the group, is wanting or replaced by a low ridge. The general colour of the surface is dark grey above and white below, but variously marbled and spotted with different shades of grey.

The narwhal is essentially an Arctic animal, frequenting the icy circumpolar seas, and but rarely seen south of 65° N. lat. Three instances have, however, been recorded of its occurrence on the British coasts, one in the Firth of Forth in 1648, one near Boston in Lincolnshire in 1800, while a third, which entangled itself among rocks in the Sound of Weesdale, Shetland, in September 1808, is described by Fleming in the Memoirs of the Wernerian Society, vol. i. Like most other cetaceans it is gregarious in its habits, being usually met with in " schools " or herds of fifteen or twenty individuals. Its food appears to be various species of cephalopods, small fishes, and crustaceans. The purpose served in the animal's economy by the wonderfully developed asymmetrical tusk - or " horn," as it is commonly but erroneously called - is not known. As it is present only in the male sex, no function essential to the wellbeing of the individual, such as the procuring of sustenance, can be assigned to it, but it must be looked upon as belonging to the same category of organs as the antlers of deer, and perhaps may be applied to similar purposes. Very little is, however, known of the habits of narwhals. Scoresby describes them as " extremely playful, frequently elevating their horns and crossing them with each other as in fencing." They have never been known to charge and pierce the bottom of ships with their weapons, as the swordfish, a totally different animal, often does. The name " Sea Unicorn," sometimes applied to the narwhal, refers to the resemblance of its tusk to the horn represented as projecting from the forehead of the fabled unicorn. The ivory of which the tusk is composed is of very good quality, but, owing to the central cavity, is only fitted for the manufacture of objects of small size. The entire tusks are sometimes used for decorative purposes, and are of considerable, though very fluctuating, commercial value. (w. H. F.)