WHALES, PORPOISES, AND DOLPHINS. 179 



single tusk of the males is always the left one, the right remaining, as a rule, 

 undeveloped in the gum ; but occasionally specimens are found with two 

 tusks. Besides these tusks there are no other functional teeth in the males, 

 and the females are toothless. The length of the head and body varies from 

 12 to 16 ft. and that of the tusk between 7 and 8 ft. Allied to the narwhal is 

 the beautiful white-whale or beluga {Delphinapterus leucas), which is likewise 

 a northern form, and also the sole representative of its genus. It may be 

 recognised by its pure glistening white skin, the absence of a tusk, and the 

 presence of numerous teeth in the front of the jaws. The beluga, which 

 congregates in troops of considerable s'ze, is regularly hunted for the sake of 

 its hide, blubber, and flesh ; the latter being dried and eaten by the Green- 

 landers and Eskimos, as well as by the sledge-dogs of the latter. 



In ordinary language the term porpoise is applied to many of the members 

 of the present family, but in a scientific sense it is confined to the members 

 of the small genus Phocmna, all of which are comparatively small-sized ceta- 

 ceans, characterised by possessing from sixteen to twenty-six pairs of small, 

 short, somewhat spade-shaped teeth. In the common porpoise {P. communis) 

 of the European seas the back is furnished with a well-developed fin ; but in 

 the Indian species (P. phocoenoides) this appendage is wanting. Porpoises 

 are the most confimon and familiar of all cetaceans, their rolling gambols 

 being well known not only to all those who have m.ade a voyage, but likewise 

 to visitors to the sea-side. The allied genus Cephalorhmichtis is typified by 

 Heaviside's dolphin (0. heavisidei), and includes four species from the Southern 

 seas. They have a conical head, without any distinct beak, and from twenty- 

 five to thirty-one pairs of small and sharp teeth. The back-fin is triangular 

 or ovate ; and in three out of the four species the flippers have a characteristic 

 elliptical shape. Externally their most distinctive feature is the coloration, 

 the upper-parts being black, and the under surface of the body white, with 

 the white area terminating on the under side of the tail in a trident, the 

 lateral prongs of which run obliquely upwards on the flanks a little behind the 

 back-fin. The Irawadi dolphin {Orcella Jiumincdis), of which a variety, or 

 perhaps an allied species, occurs in the Bay of Bengal and some of the 

 neighbouring seas, represents a genus distinguished by the glo-bose, beakless 

 head, and the small size and number of the teeth, the latter occupying nearly 

 the entire length of the jaws, and including from thirteen to seventeen pairs 

 in the upper, and from twelve to fifteen in the lower jaw. They are set close 

 together, and are conical and pointed in shape, those in the front of the jaws 

 of the adult males being inclined outwards. The moderate-sized flippers are 

 broad at the base, and of a subovate contour ; while the back-fin is small and 

 hooked. From 7 to 7j ft. is the usual length of these dolphins, which are 

 either blackish or slaty in colour. 



From all the preceding the large and strikingly-coloured cetaceans known 

 as killers, or grampuses {Orca), differ by the large size of their powerful 

 conical teeth, which are crowded together, and usually form twelve pairs in 

 each jaw. And they are further characterised by the great vertical height of 

 the back-fin. As regards colour, the upper-parts and flippers are black and 

 the lower surface whitish ; the white area ending on the under side of the 

 tail in a trident, very nearly the same as in the above-mentioned genus 

 Cephalorhynchus. Above and behind the eye is a white streak, and there 

 is a purplish band across the back behind the fin. Killers, of which 

 there is but a single well-defined species, grow to a length of at least 20 ft., 

 and enjoy an almost cosmopolitan distribution, They derive their popular 



