[Illustration: 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, _D. 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 American coast as the river St. Lawrence, which it ascends for a considerable distance. On rare occasions it has been seen on the coast of Scotland. Remains of a Cetacean from the Lower Pliocene of Tuscany have been referred by Brandt to this genus under the name _D. brocchii_. In all the remaining genera of _Delphinidæ_ the cervical region of the vertebral column is very short, and the first two, and usually more, of the vertebræ are firmly united. _Phocæna._[157]—Teeth ²⁵⁄₂₅, small, occupying nearly the whole length of the rostrum, with compressed, spade-shaped crowns, separated from the root by a constricted neck (Fig. 92). Rostrum rather shorter than the cranium proper, broad at the base and tapering towards the apex. Premaxillæ raised into tuberosities in front of the nares. The frontal bones forming a somewhat square, elevated protuberance in the middle line of the skull behind the nares, rising altogether above the flattened nasals. Pterygoids very small, and widely separated in the middle line. Symphysis of mandible very short. Vertebræ: C 7, D 13, L 14, C 31; total 65 (subject to slight individual variations). First to sixth cervical vertebræ, and sometimes the seventh also, coalesced. Manus of moderate size, oval, slightly falcate; second and third digits nearly equal in length; fourth and fifth well developed, but shorter. Dorsal fin near the middle of the back, triangular; its height considerably less than the length of the base; its anterior edge frequently furnished with one or more rows of conical horny tubercles. [Illustration: FIG. 92.—Teeth of Porpoise. Twice natural size.] The common Porpoise (Fig. 93), _P. communis_, is the best known of British Cetaceans. The word Porpoise (sometimes spelled Porpus and Porpesse) is apparently derived from the French _porc_ and _poisson_, or the Italian _porco_ and _pesce_, and thus corresponds with some of the English vernacular appellations, “hog-fish,” “sea-hog,” “herring-hog,” and the German _Meerschwein_, whence the usual modern French name of the animal, _marsouin_. “Porpoise” is commonly used by sailors to designate all the smaller Cetaceans, especially those numerous species which naturalists call “Dolphins”; but in scientific language it is restricted to the genus _Phocæna_ of Cuvier, of which the Porpoise of the British seas, _Phocæna communis_, Cuvier (_Delphinus phocæna_, Linnæus), is the type.