NARWHAL  , the Scandinavian name of a cetacean (Monodon monoceros), characterized by the presence in the male of a

long horn-like tusk . In the adult of both sexes there are only two teeth, both in the upper jaw, which lie horizontally side by side, and in the female remain throughout life concealed in cavities of the bone . In the male the right tooth usually remains similarly concealed, but the left is immensely developed, attaining a length equal to more than half that of the entire animal . In a narwhal 12 ft. long, from snout to end of tail, the exserted portion of the tusk may measure 6 or 7 and occasionally 8 ft. 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 spiral 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 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 young animals several small additional teeth 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 the beluga) a dorsal fin, found in nearly all other members of the group, is wanting . The general colour of the surface is dark grey above and white below, variously marbled and spotted with shades of grey . The narwhal is an Arctic whale, frequenting the icy circumpolar seas, and rarely seen south of 65° N. lat . Four instances have, however, been recorded of its occurrence on the British coasts, one on the coast of Norfolk in 1588, one in the Firth of Forth in 1648, one near Boston in Lincolnshire in 1800, while a fourth entangled itself among rocks in the Sound of Weesdale, Shetland, in September 18o8 .

Like most cetaceans it is gregarious and usually met with in "

schools " or herds of fifteen or twenty individuals . Its food appears to be cuttlefishes, small fishes and crustaceans . The purpose served by the tusk—or " horn "—is not known; and little is 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 does . The name " sea-unicorn " is sometimes applied to the narwhal . The ivory of which the tusk is composed is of very good quality, but owing to the central cavity, only fitted for the manufacture of objects of small size . The entire tusks are sometimes used for decorative purposes, and are of considerable, though fluctuating, value . (See CETACEA.) (W . H .