262 CETACEA 
in the male sex, no function essential to the well-being 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 cate- 
gory 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 
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, which extends the greater part of 
its length, 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. 
Delphinapterus.A—This genus is closely allied to the last in ex- 
ternal form, as well as anatomical structure, differing mainly in the 
very distinct character of the dentition. Teeth from § to +9, 
occupying the anterior three-fourths of the rostrum and correspond- 
ing portion of the mandible, rather small, conical, and pointed 
-when unworn, but usually becoming obliquely truncated, separated 
by intervals considerably wider than the diameter of the tooth, and 
implanted obliquely, the crowns inclining forwards, especially in 
the upper jaw. Skull rather narrow and elongated, depressed. 
Premaxille convex in front of the nares. Rostrum about equal in 
length to the cranial portion of the skull, triangular, broad at the 
base, and gradually contracting towards the apex, where it is some- 
what curved downwards. Vertebre: C7,D 11, L 9, C 23; total 50. 
Cervical vertebra free. Manus broad, short, and rounded, all the 
digits being tolerably well developed, except the first. No dorsal 
fin, but a low ridge in its place. 
Fic. 91.—Beluga or White Whale (Delphinapterus leucas). From a specimen taken in the river 
St. Lawrence, and exhibited in London, 1877. 
One existing species, D. lewcas (Fig. 91), the Beluga or White 
Whale, so called from its pure white colour, about 12 feet long, 
abundant in the Arctic seas, and extending as far south on the 
1 Lacépéde, Hist. Nat. des Cétacés, p. xli. (1804). 
