the relationships of which are by no means clearly
apparent. The first section is that of the whalebone whales, or
Mystacoceti, in which no functional teeth are developed, although
there are tooth-germs during foetal life. The palate is furnished with
plates of baleen or whalebone; the skull is symmetrical; and the nasal
bones form a roof to the nasal passages, which are directed upwards
and forwards. The maxilla is produced in front of, but not over, the
orbital process of the frontal. The lacrymal is small and distinct
from the jugal. The tympanic is welded with the periotic, which is
attached to the base of the skull by two strong diverging processes.
The olfactory organ is distinctly developed. The two halves of the
lower jaw are arched outwards, their anterior ends meeting at an
angle, and connected by fibrous tissue without any symphysis. All the
ribs at their upper extremity articulate only with the transverse
processes of the vertebrae; their capitular processes when present not
articulating directly with the bodies of the vertebrae. The sternum is
composed of a single piece, and articulates only with a single pair of
ribs; and there are no ossified sternal ribs. External openings of
nostrils distinct from each other, longitudinal. A short conical
caecum.

When in the foetal state these whales have numerous minute teeth lying
in the dental groove of both upper and lower jaws. They are best
developed about the middle of foetal life, after which they are
absorbed, and no trace of them remains at the time of birth. The
whalebone does not make its appearance until after birth; and consists
of a series of flattened horny plates, between three and four hundred
in number, on each side of the palate, with a bare interval along the
middle line. The plates are placed transversely to the long axis of
the palate, with short intervals between them. Each plate or blade is
somewhat triangular in form, with the base attached to the palate and
the apex hanging downwards. The outer edge of the blade is hard and
smooth, but the inner edge and apex fray out into long bristly fibres,
so that the roof of the whale's mouth looks as if covered with hair,
as described by Aristotle. At the inner edge of each principal blade
are two or three much smaller or subsidiary blades. The principal
blades are longest near the middle of the series, and gradually
diminish towar