GHT WHALES_.

They are distinguished from the last group by their enormous heads,
with more symmetrical skulls, the facial portion of which is greatly
in excess of the cranial. The bones of the lower jaw are not united
at the symphysis, but are held together by strong fibrous bands; the
two rami are very much rounded and arched outwards; there are no teeth.
The maxillary and premaxillary bones are much produced, forming a
rostrum tapering, narrow, compressed and much arched in the right
whales. From this depends the mass of whalebone, which grows from
a fleshy substance "similar," as is aptly described by Dr. Murie,
"to the roots of our finger-nails. It grows continuously from the
roots like the latter, and in many respects corresponds, save that
the free end is always fringed. Baleen, therefore, though varying
from a few inches to a number of feet long, in fact approximates to
a series of, so to say, mouth nail-plates, which laminae have a
somewhat transverse position to the cavity of the mouth, and thus
their inner split edges and lower free ends cause the mouth to appear
as a great hairy archway, shallower in front and deeper behind"
(Cassell's Natural History).

The object of this vast amount of whalebone is to strain from the
huge gulps of water the mollusca, &c., on which this animal feeds.
The tongue of these whales is very large, filling up the space between
the lower jaws. The gullet is small in comparison. The nasal aperture
differs from the _Denticete_ in being symmetrical, that is, having
the double aperture, and in being directed forwards as in most
mammals, instead of upwards and backwards as in the dolphins. The
whale produces generally one at a birth, which it suckles for some
length of time. The mammae are pudendal. The right whales have no
fin on the back; those that have form a separate genus, Balaenoptera,
i.e. fin-whales.

They are the most valuable of the cetacea, except perhaps the
cachelot or sperm whale, as producing the greatest amount of oil and
whalebone. Of the various species the most sought after is the
Greenland or right whale (_Balaena mysticetus_), which ordinarily
attains a length of fifty to sixty feet. An average whale between
forty and fifty feet in length will yield from sixty to eighty barrels
of oil and a thousand pounds of baleen.

[Illustration: Skull of Baleen Whale. Br, brain cavity; J J*, upper
and lower jawbones; the arrows indicate narial passages; S,
spout-hole; W,