Rudolphi's Rorqual (B. borealis) seems to be a perfectly inoffensive beast; it is said to be able to stay under water for as long a time as twelve hours.
A smaller species than the last is B. rostrata—at the outside 33 feet in length. Here the hairy covering is reduced[[227]] 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.[[228]]
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,[[229]]
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[[230]] 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.
Rhachianectes, with but one species, R. glaucus,[[231]] the "Californian Grey Whale," is the last genus of the family Balaenopteridae. This Whale is but imperfectly known anatomically; but quite sufficient has been ascertained to show its great divergence from Balaenoptera or Megaptera. The dorsal fin is completely absent, and the throat pleats, so characteristic of the typical Balaenopteridae, are reduced to two. It has, however, the general outline of a Rorqual, with a relatively small head. In osteological characters it tends to unite the two families Balaenopteridae and Balaenidae (if they are really necessary subdivisions). The skull is on the whole Rorqual-like; but its fore-part is narrow as in the Greenland Whale, and the premaxillaries are pinched up in the middle line so as to be visible from the side; this again is a Balaenid character. The cervical vertebrae are free as in Rorquals, and the sternum is quite as in that group. The scapula has more the shape of that of Balaena.
Rhachianectes glaucus is confined to the Pacific, and has been extensively hunted from the shore. It is not, however, a very valuable Whale, since the baleen is short as in Rorquals, and the
beast, moreover, appears to be fierce, a somewhat rare attribute of Whales. It has been spoken of, indeed, as "a cunning, courageous, and vicious" animal. Rhachianectes is essentially a coast Whale, and loves to lie in the surf in quite shallow water waiting for the tide to float it off. This Whale varies much in colour from black to mottled grey and black, and reaches a length of about 40 feet.
Fam. 2. Balaenidae.—The Right Whales of the genus Balaena are to be distinguished from Neobalaena and from the Rorquals by the following characters:—
The size is large, 50 to 60 feet. There is no dorsal fin. The head is more than or nearly one-fourth of the entire length of the animal. The baleen is very long. The throat is not grooved. The orbital process of the frontal is not wider than the downward process of the maxilla. The cervical vertebrae are all fused. The scapula is rather high. The hind-limb has the rudiment of a tibia. The intestine has no caecum.