m mainly to the
accumulation of a mass of fatty tissue filling the large hollow on the
upper surface of the skull and overlying the long muzzle. The single
blow-hole is longitudinal, slightly S-shaped, and placed at the upper
and anterior extremity of the head to the left side of the middle
line. The opening of the mouth is on the under side of the head,
considerably behind the end of the snout. Flippers short, broad and
truncated. Dorsal fin represented by a low protuberance. See
SPERM-WHALE.

[Illustration: FIG. 2.--Skull of Sperm-Whale (_Physeter
macrocephalus_).]

In the lesser or pigmy sperm-whale (_Cogia breviceps_) there may be a
pair of rudimentary teeth in the upper jaw, while on each side of the
lower jaw there are from 9 to 12 rather long, slender, pointed and
curved teeth, with a coating of enamel. Upper surface of the skull
concave, with thick, raised, posterior and lateral margins, massive
and rounded at their anterior terminations above the orbits. Muzzle
not longer than the cranial position of the skull, broad at the base,
and rapidly tapering to the apex. Zygomatic process of the jugal
rod-like. Lower jaw with symphysis less than half its length.
Vertebrae: C 7, D 13 or 14, L and Ca 30; total 50 or 51. All the
cervical vertebrae united by their bodies and arches. The head is
about one-sixth of the length of the body, and obtusely pointed in
front; the mouth small and placed far below the apex of the snout; the
blow-hole crescentic, and placed obliquely on the crown of the head in
advance of the eyes and to the left of the middle line; while the
flippers are bluntly sickle-shaped, and the back-fin triangular. This
species attains a length of from 9 to 13 ft.

[Illustration: FIG. 3.--Bottle-nose (_Hyperoodon rostratus_). From a
specimen taken off the coast of Scotland, 1882.]

A second subfamily is represented by the bottle-noses and beaked
whales, and known as the _Ziphiinae_. In this group the lower teeth
are rudimentary and concealed in the gum, except one, or rarely two,
pairs which may be largely developed, especially in the male. There is
a distinct lacrymal bone. Externally the mouth is produced into a
slender rostrum or beak, from above which the rounded eminence formed
by a cushion of fat resting on the cranium in front of the blow-hole
rises somewhat abruptly. The blow-hole is single, crescentic and
median, as in th