narwhal or " sea-unicorn " (lifonodon monoceros) is also an inhabitant of the Arctic seas. The tusks are reduced to a single tooth, restricted to the male. It grows from the upper jaw, in a straight line ; its exterior is marked by spiral ridges, which wind from within, forwards, upwards, and to the left. About 14 in. is implanted in the socket, and this is the most solid and weighty portion ; it tapers gradually from base to apex, and attains a length of 9-10 ft., and a diameter of 4 in. at the base. It is, in fact, the left tusk of a pair, the right one being abortive, but always to be found in a rudimentary state, and occasionally protruding for a few inches. Denmark has sometimes imported 100 tons of these tusks (miscalled " sword-fish horns") from the Arctic seas in one year. The Greenland Co. collected 457 lb., valued at 175/., in the year ending March 1875. The substance of the tusk is comparatively coarse, and of little value.
Dugong-ivory.—The Australian "dugong" (Halicore australis) is best known as affording a valuable animal oil, and is therefore described at length under Oils ; but it also yields a kind of ivory. According to some accounts, the intermaxillary bones of the animal possess a fineness and hardness of grain, specific gravity, and appearance closely resembling ivory, and may be generally used as a substitute for elephant-ivory. Other accounts speak only of the two large incisor teeth or tusks, which adorn the head of the male, as being suitable for such purposes. Some cwt. have formerly been shipped from Moreton Bay, and valued at 60s. a cwt.
Imports and Values of Ivory.—Our imports of ivory—designated, in the Custom-House Returns, as elephants', sea-cows' and sea-horses' " teeth " (the commercial term being, in this case, scientifically correct)—in 1879 were as follows :—From Holland, 580 cwt., 23,876/. ; Malta, 648 cwt., 26,203/. ; Egypt, 685 cwt., 37,530/. ; Aden, 440 cwt., 21,505/. ; E. coast Africa, native states, 650 cwt., 32,511/. ; British S. Africa, 1367 cwt., 62,772/. ; British W. Africa, 85 cwt., 3337/. ; W. coast Africa, Portu guese possessions, 275 cwt., 11,613l.; W. coast Africa, not particularly designated, 1801 cwt., 69,798/.; Bombay and Scinde, 1737 cwt., 79,065/. ; Bengal and Burmah, 55 cwt., 2625/. ; other countries, 1091 cwt., 36,092/. ; total, 9414 cwt., 406,927/.
The approximate relative values are :—Elephant-ivory : 70 lb. each, and upwards, 50-701. a cwt. ; 50-70 lb., or " seconds," 45-65/. ; 35-50 lb., or " thirds," 40-60/. ; 20-35 lb., or " fourths," 30-50/. ; " ecrivelloes," 12-34/. ; solid scrivelloes for billiard-balls, 45-65/. ; cut pieces for billiard-balls, 50-751. Sea-horse (walrus) teeth, 6d.-8s. a lb.
The chief substitutes for ivory are an artificial compound termed "celluloid," and the hard vegetable kernels called " corozo-nuts." Bibliography.—R. Owen, Ivory and Teeth of Commerce' (Jour. Soc. Arts, Vol. v., No. 213, Loudon : 1856); P. L. Simmonds, Animal Products' (London : 1877).
(See Bones ; Celluloid ; Horn ; Nuts—Corozo-nuts).