PORPOISE (sometimes spelled Porpus and Porpesse)  , a name derived from the O . Fr. porpeis, for port-peis, i.e. pig-fish, Lat. porcus, pig, and piscis, fish; the mod . Fr. marsouin is borrowed from the Ger. meerschwein, although the word is commonly used by sailors to designate all the smaller cetaceans, especially those numerous species which naturalists call " dolphins," it is properly restricted to the common porpoise of the British seas (Phocaena communis, or P. phocaena) . The porpoise, when full grown, attains a length of 5 ft. or more; the dimensions of an adult female specimen from the t~ . -- English Channel being: length from nose to notch between the flukes of the tail, 624 in.; from the nose to the front edge of the dorsal fin, 29 in.; height of dorsal fin, 4i in.; length of base of dorsal fin, 8 in.; length of pectoral fin, g; in.; breadth of pectoral fin, 3i in.; breadth of tail flukes, 13 in . The head is rounded in front, and differs from that of dolphins in not having the snout produced into a distinct " beak " separated from the forehead by a groove . The under jaw projects about half an inch beyond the upper .. The mouth is wide, bounded by stiff immobile. lips, and curves slightly upwards at the hinder end . The eye is small, and the external ear represented by a minute aperture, scarcely larger than would be made by a pin, about 2 in. behind . the eye . The dorsal fin, near the middle of the back, is low and triangular . The flippers are of moderate size, and slightly sickle-shaped . The upper-parts are dark grey or nearly black according to the light in which they are viewed and the state of moisture or otherwise of the skin; the under-parts pure white .

The

line of demarcation between these colours is not distinct, washes or splashes of grey encroaching upon the white on the sides, and varies some-what in different individuals . Usually it passes from the throat (the anterior part of which, with the whole. of the under jaw, is dark) above the origin of the flipper, along the middle of the flank, and descends again to the middle line 'before reaching the tail . Both sides of the flippers and flukes are black . The anterior edge of the dorsal fin is furnished with a row of small rounded horny spines or, rather, tubercles, of variable number . One of the most characteristic anatomical distinctions between the porpoise and other members of the Delphinidae is the form of the teeth (numbering twenty-three to twenty-six on each side of each jaw), which have expanded, flattened, spade-like crowns, with more or less marked vertical grooves, giving a tendency to a bilobed or often trilobed form (fig . 2) . The porpoise, which is sociable and gregarious, is usually seen in small herds, and frequents coasts, bays and estuaries rather than the open ocean . It is the commonest cetacean in the seas round the British Isles, and not infrequently ascends the Thames, having been seen as high as Richmond; it has also been observed in the Seine at Neuilly, near Paris . It frequents the Scandinavian coasts, entering the Baltic in the summer; and is found as far north as Baffin's Bay and as far west as the coasts of the United States . Southward its range is more limited than that of the dolphin, as, though common on the Atlantic coasts of France, it is not known to enter the Mediterranean . It feeds on mackerel, pilchards and herrings and, following the shoals, is often caught by fishermen in the nets along with its prey . In former times it was a common article of food in England and France, but is now rarely if ever eaten, being valuable only for the oil obtained from its blubber .

Its skin is sometimes used for

leather and boot-thongs, but the so-called " porpoise-hides " are generally obtained from the beluga . The Black Sea porpoise (P. relicta) is a distinct species . A third species, from the American coast of the North Pacific, has been described under the name of Phocaena vomerina, and another from the mouth of the Rio de la Plata as P. spinipennis . Nearly allied is Neophocaena phocaenoides, a small species from the Indian Ocean and Japan, with teeth of the same form as those of the porpoise, but fewer in number (eighteen to twenty on each side), of larger size, and more distinctly notched or lobed on the free edge . It is distinguished from the common porpoise externally by its black hue and the absence of a dorsal fin . (See CETACEA.) (R .