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. 

 Dclpldnapternx. 1 — 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 f- to \%, 

 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. 

 Premaxillae 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- 

 Avhat curved downwards. Vertebra? : C 7, D 11, L 9, C 23 ; total 50. 

 Cervical vertebrae 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. 



Fig. 91.— Beluga or White Whale (Delphinapterus leucas). From a specimen taken in the river 

 St. Lawrence, and exhibited in London, 1877. 



One existing species, I), leucas (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 



Lacepede, Hist. Nat. dcs Citads, p. xli. (1S04). 



