The Whale commonly called “Humpback” (_Megaptera boops_) by whalers, perhaps on account of the low hump-like form of the dorsal fin, is very distinctly characterised from all others of the group, especially by the immense length of the pectoral fins or flippers, which are indented or scalloped along their margins, and are, except at their base, of a white colour, nearly all the rest of the body being black. The baleen plates are of a deep black colour. Though common in the North Atlantic between Norway and Greenland, this Whale does not frequently appear on the coasts of the British Isles. One came ashore at Newcastle in 1839; another, a young one, was taken in the estuary of the Dee in 1863, and its skeleton is preserved in the Liverpool museum; and a nearly full-grown animal was captured in the mouth of the Tay in the winter of 1883-84.[135] The usual length of the adult ranges from 45 to 50 feet, the female being larger than the male. Whales of the genus _Megaptera_ are found in the South Atlantic and in both the North and the South Pacific. They resemble those of British seas so closely that it is doubtful whether the differences which have been observed, and upon which several species have been founded, may not be individual peculiarities; but zoologists have not yet had the opportunity of examining and comparing such a series of specimens of different ages and sexes from different localities as would be necessary to determine these points satisfactorily. [Illustration: FIG. 79.—Humpbacked Whale (_Megaptera boops_).] Tympanic bones of _Megaptera_ occur in the English and Belgian Crags, although somewhat less commonly than those of _Balæna_ and _Balænoptera_; they have been described under the names of _Megapteropsis_ and _Burtinopsis_. [Illustration: FIG. 80.—The Common Rorqual (_Balænoptera musculus_).] _Balænoptera._[136]—Head small and flat, and pointed in front. Body long and slender. Skin of throat plicated. A small falcate dorsal fin. Baleen short and coarse. Cervical vertebræ free. Scapula low and broad, with a large acromion and coracoid process. Pectoral limb tetradactylous, small, narrow, and pointed. Tympanic (Fig. 81) long, much inflated, and rounded, with the involuted portion thickened and pyriform, and the notch for the Eustachian canal sharply defined; inner surface flattened, without the vertical groove found in _Megaptera_. [Illustration: FIG. 81.—The right tympanic of _Balænoptera musculus_ from the inner (A) and outer (B) aspects. ½ natural size. (From the _Proc. Zool. Soc._)]