The Dolphins and Porpoises, as already stated, embrace the greater number of existing species of Whales. Sir W. Flower and others who have followed him, allow nineteen genera. But as to the exact number of known species there is much uncertainty. That very careful observer, Mr. True, considers[256] that there are fifty which demand recognition. As many as one hundred have received names. The matter is one which is perhaps barely ripe for decision. All the Dolphin tribe are, for Whales, smallish animals. The Killer Whale, _Orca_, is the only genus (or species?) which usually attains to more than moderate bulk. The rather mysterious _Delphinus coronatus_, 36 feet in length, of M. de Freminville, would seem to be a Ziphioid; it was described as having a very pointed beak, and as having the dorsal fin situated near the tail; such characters suggest a _Mesoplodon_. The genus _Delphinapterus_, the Beluga or White Whale, consists of but a single species, though as usual more than one name has been given to supposed different species. It is characterised as a genus by the following assemblage of structural features:--It has only eight to ten teeth occupying the anterior part of the jaws only. All the cervical vertebrae are free and unjoined. The vertebral formula is C 7, D 11 (or 12), L 9, Ca 23. The pterygoids are wide apart, though they converge as if about to meet at their posterior ends. There is no dorsal fin. The colour is white. {373} The Beluga is a northern species purely. The reputed form, _D. kingii_, was said to come from Australian seas; but there seems to have been an error in this statement. It is interesting to note that the white colour, so characteristic of the genus and species, is not found in the young, which are blackish. They gradually pale as they advance towards maturity. _Delphinapterus leucas_ reaches a length of 10 feet, and like other Porpoises will ascend rivers in search of food. It is said to be specially addicted to salmon. Among the contents of the stomach have been found quantities of sand. But this habit of swallowing sand or pebbles has been noted in other Whales. Whether it is or is not accidental (taken in with ground-living food), it seems hardly likely that it is used for purposes of ballast! The Beluga has a voice; but the name "Sea Canary" is hardly suitable to it. A specimen of this species, recently described from the shores of Scotland (it is often thrown up upon our coasts), which had got entangled in the stakes of a new net, was regarded by the natives, on account of its white colour, as a ghost. Externally, besides its colour, the Beluga is remarkable for possessing a distinct neck, which is correlated of course with the freedom of the cervical vertebrae, and is also seen in Platanistidae.