eldom enters the Mediterranean, and apparently never resides there.
There is, however, a porpoise in the Black Sea, which, according to Dr
O. Abel, is entitled to rank as a distinct species, with the name of
_Phocaena relicta_. This Black Sea porpoise is readily distinguished
from the Atlantic species by the contour of the profile of the head,
which, in place of forming a continuous curve from the muzzle to what
represents the neck, has a marked prominence above the angle of the
mouth, followed by an equally marked depression. The teeth are also
different in form and number. The absence of porpoises from the
Mediterranean is explained by Dr Abel on account of the greater
saltness of that sea as compared with the ocean in general; his idea
being that these cetaceans are near akin to fresh-water members of the
group, and therefore unsuited to withstand an excessively saline
medium. From the Taman Peninsula, on the north shore of the Black Sea,
the same writer has described an extinct type of ancestral porpoise,
under the name of _Palaeophocaena andrussowi_. Another species is the
wholly black _P. spinipennis_, typically from South America. Black is
also the hue of the Indian porpoise (_Neophocaena phocaenoides_),
which wants a dorsal fin, and has eighteen pairs of teeth rather
larger than those of the ordinary porpoise. (See PORPOISE.)

[Illustration: FIG. 9.--Beluga or White-Whale (_Delphinapterus
leucas_). From a specimen taken in the river St Lawrence and exhibited
in London, 1877.]

Next comes the Indo-Malay genus _Orcella_, in which the 12/12 to
14/14, small, conical teeth are pointed, rather closely set, and
occupy nearly the whole length of the rostrum. Skull sub-globular,
high. Rostrum nearly equal in length to the cranial portion of the
skull, tapering. Flippers of moderate size, not elongated, but
somewhat pointed, with all the bones of the digits broader than long,
except the first phalanges of the index and third fingers. Head
globular in front. Dorsal fin rather small, placed behind the middle
of the body. Two species, both of small size--_O. brevirostris_, from
the Bay of Bengal, and _O. fluminalis_, from the Irrawaddy river, from
300 to 900 m. from the sea.

In the grampus, or killer, _Orca gladiator_ (or _O. orca_) the teeth
form about twenty pairs, above and below, occupying nearly the whole
length of the rostrum, very large and sto