A smaller species than the last is _B. rostrata_--at the outside 33 feet in length. Here the hairy covering is reduced[237] to "two small hairs on the integument covering the apex of the lower maxilla." The colour is greyish black above, the underside white. On the other hand, _B. sibbaldii_, the Blue Whale, is the giant of its race, reaching a length of 85 feet. Its colour is a dark bluish grey, with small whitish spots on the breast. The dorsal fin is small and low with straight margins. _B. musculus_, the Finner, is intermediate in size--not more than 70 feet. It seems doubtful whether the "sulphur bottom," _B. australis_, of Antarctica and _B. patachonica_ differ specifically from this.[238] The genus _Megaptera_ is very near _Balaenoptera_, but differs from it mainly in the following external and internal characters. The dorsal fin is not very prominent, and its place is taken by a lowish hump, whence, indeed, the common name of this Whale, "Humpback." The pectoral fin is unusually long, and the creature uses it to beat itself, the surrounding water, and, more playfully, its mates. The general outline of this Cetacean is more clumsy than that of _Balaenoptera_. The most important internal difference is in the form of the scapula, which has at most a slight acromion and coracoid process. These are rather more pronounced, according to Messrs. van Beneden and Gervais,[239] {357} in the southern form of the genus, which is known as _M. lalandii_. The head, it should also be remarked, is studded with large tubercles about the size of an orange, which seem to be hyper-trophied rudiments of the hairs, which should be present in this region of the body. As is the case with other Whales, numerous species have been made out of individuals of _Megaptera_. Captain Scammon, who observed many "gams" or herds of these Whales, remarked[240] that he had extreme difficulty in finding any two individuals precisely alike! The best-known species in any case is the northern _M. longimana_, which occurs on our own coasts. The genus is, like so many Cetaceans, world-wide in range; and it is possible that the difference in the scapula already referred to may justify the separation of a southern _M. lalandii_ (with which in that case, perhaps, _M. capensis_ and _M. novae zelandiae_ will be synonymous). Quite recently M. Gervais has insisted upon a _Megaptera indica_ from the Persian Gulf. _Megaptera_ grows to a length of 50 to 60 feet. Seventy-five feet have been stated, but measurements of Whales have usually to be received with caution.