The Mystacoceti are nearly invariably huge creatures, the sole exceptions being the Pygmy Right Whale, Neobalaena, and
a small Rorqual. But even these are larger than the majority of Toothed Whales.
The most characteristic feature by which the Whalebone Whales are to be distinguished from other Whales is that which gives to them their name, the presence of whalebone. Whalebone is a horny product of the epithelium lining the mouth, and is comparable to an exaggeration of the transverse ridges which are found in the mouths of all mammals upon the palate. In non-Cetacean mammals these ridges vary in depth, and are arranged as a rule transversely, but with an oblique inclination. This is precisely how the plates of baleen are disposed in the mouth of a Whale. Each piece of "bone" is triangular in shape, the broader end being that of attachment while it narrows gradually; the inner side of the blades is frayed out into a number of threads which form the straining apparatus. The plates vary in length up to as great an extreme length as 13 feet, which occurs in the Right Whale at times. The colour is black or paler, even white. The number of these plates in the mouth is very great. As many as 370 blades have been counted. They diminish in length towards both ends of the series. Though whalebone has been in use for a long period, whence the whalebone came was formerly one of those things not generally known.
Fig. 189.—Section of upper jaw, with baleen plates, of Balaenoptera. a, Bone of jaw; b, gum; c, straight edge of baleen plate; d, e, frayed out surface of baleen plates. (After Owen.)
A very prevalent notion was that the whalebone formed the eyelids or perhaps the eyelashes of the creature. Scaliger, commenting upon Aristotle, held that the whale had "lamellae upon the eyebrows, which, when the head is plunged below the surface, were raised by the water; but when the animal raised its head
above the waves the lamellae fell and covered the eyes." Whalebone, too, has been often spoken of as "the fin of a whale," "the finnes that stand forth of their mouths." The value of whalebone is still great, in spite of various substitutes which are now used in its place. In the year 1897, for example, the value of this article was £2000 per ton. As a single Whale may produce several tons of this material, it is not surprising to find that the results of a whaling voyage may be very profitable.
Fam. 1. Balaenopteridae.—This genus Balaenoptera includes the Rorquals, which are Whalebone Whales of large size, differing from the Right Whales in three important external characters: the head is comparatively small; there is a dorsal fin; the throat is marked by numerous longitudinal furrows. The bones of the cranium are not so arched as in the Right Whales, and as a consequence the plates of baleen are shorter. The hand is only four-fingered. The cervical vertebrae are for the most part all free. One of the earliest records of a Whale stranded in the Thames was probably of a species of this genus in the year 1658, and is thus described by John Evelyn:—"A large whale was taken betwixt my land butting on the Thames and Greenewich, which drew an infinite concourse to see it, by water, horse, coach, and on foot, from London and all parts.... It was killed with a harping yron, struck in the head, out of which spouted blood and water by two tunnells, and after an horrid grone it ran quite on shore and died. Its length was 58 foot, heighth 16; black skinn'd like coach leather, very small eyes, greate taile, onely two small finns, a picked snout, and a mouth so wide that divers men might have stood upright in it; no teeth, but suck'd slime onely as thro' a grate of that bone which we call whalebone, the throate yet so narrow as would not have admitted the least of fishes ... all of it prodigious, but in nothing more wonderful that an animal of so greate a bulk should be nourished onely by slime thro' those grates."
Professor Collett has recently given[[226]] an elaborate account of the characters and habits of this great Whale (Balaenoptera musculus). Though a large beast (44 to 67 feet in length) it is exceeded by other Rorquals; it is of a dark grey blue colour above, white, for the most part, below. The dorsal fin is large and high; the flippers relatively slender and small. The whole throat from the
symphysis of the jaws to the middle of the belly is, as in other species, marked by furrows, forty to fifty-eight in number. The hairy covering is reduced (in an adult female) to thirteen hairs on each side of the lower jaw; in a foetus there were also seven hairs on each side of the upper jaw, as well as rather more on the lower jaw—altogether, forty-eight. This Whale appears to feed chiefly upon small Crustacea, especially the Copepod, Calanus finmarchicus. The number of baleen plates is about 330 on each side of the jaw. This Whale sometimes swims singly, but usually in schools of even as many as fifty.