Delphinida.—This family includes the Dolphins, Porpoises, and Narwhal,
and is characterized by usually possessing teeth in both jaws
includes the Dolphins, Porpoises, and Narwhal, and is characterized by
usually possessing teeth in both jaws : the teeth being numerous, and
conical in shape. The nostrils, as in the last family, are united, but they
are placed further back, upon the top of the head. The single blow-hole or
nostril is transverse and mostly crescentic or lunate
in shape. The head is by no means so disproportionately large as in the
former families, usually forming about one-seventh of the entire length of
Fig. 214.—The common Dolphin (Jielphinus delphis).
The most noticeable members of this family are the true Dolphins, the
Porpoises, and the Narwhal.
The Dolphins have an elongated snout, separated from the head by a
transverse depression. The common Dolphin (Delphinus ddphis, fig.
214) is the best-known species. It averages from six to eight feet in
length, and has the habit of swimming in flocks, often accompanying ships
for many miles. The female, like most of the Cetacea, is uniparous.
The Dolphin occurs commonly in all European seas, and is especially abundant
in the Mediterranean.
The common Porpoise (Phocana communis) is the commonest and smallest
of all the Cetacea, rarely exceeding four feet in length. The head is
blunt, and is not produced into a projecting muzzle. The Porpoise frequents
the North Sea, and is commonly seen off our coasts. Another British species
is the Grampus (Phocana orca), but this is much larger, attaining a
length of from eighteen to twenty feet. Nearly allied to the Grampus is the
so-called "Caing" Whale, or, as it is sometimes termed, the " Bottle-nosed"
Whale (Globicephaltts or Phoaena globiceps). This species
occurs not uncommonly round the Orkney and Shetland Islands, and attains a
length of as much as twenty-four feet . It is gregarious in its habits, and
is often killed for the sake of its oil.
Closely allied to the true Dolphins are two curious Cetaceans, belonging to
different genera, but both inhabiting fresh waters. One of these is the
Gangetic Dolphin (Platanista Gangetica), which inhabits the Ganges,
especially near its mouth. This singular animal is characterised by the
great length of its slender muzzle, and by the small size of the eyes. It
attains the length of seven feet, and the blow-hole is a longitudinal
fissure, and therefore quite unlike that of the typical Delphinida.
The other fresh-water form is the Inia Boliviensis, which
inhabits the rivers of Bolivia, and is found at a distance of more than two
thousand miles from the sea. In its essential characters it differs little
from its marine brethren, and it attains a length of from seven (female) to
fourteen feet (male). The last of the Ddphinida is the extraordinary
Narwhal or Sea-unicorn (Monodon monoceros). The Narwhal is an
inhabitant of the Arctic seas, and attains a length of as much as fifteen
feet, counting in the body alone. The dentition, however, is what
constitutes the great peculiarity of the Narwhal. The lower jaw is
altogether destitute of teeth, and the upper jaw in the females also
exhibits no teeth externally, as a general rule at any rate, though there
are two rudimentary incisors which do not cut the gum. In the males, the
lower jaw is likewise edentulous, but the upper jaw is furnished with two
molar teeth concealed in the gum, and with two incisors. Of these two upper
incisors, that of the right side is generally rudimentary, and is concealed
from view. The left upper incisor, on the other hand, is developed from a
permanent pulp, and grows to an enormous size, continuing to increase in
length throughout the life of the animal. It forms a tusk of from eight to
ten feet in length, and it has its entire surface spirally twisted. As an
abnormality, both the upper incisors may be developed in this way so as to
form projecting tusks; and it is stated that the tusk is occasionally
present in the female. The function of this extraordinary tooth is doubtless
offensive. - Manual of Zoology by HENRY
ALLEYNE NICHOLSON edited by Stanley L. Klos.
This site and its contents are not affiliated, connected,
associated with or authorized by the individual, family,
friends, or trademarked entities utilizing any part or
the subject's entire name. Any official or affiliated
sites that are related to this subject will be hyper
linked below upon submission
and Evisum, Inc. review.
Please join us in our mission to incorporate America's Four United Republics discovery-based curriculum into the classroom of every primary and secondary school in the United States of America by July 2, 2026, the nation’s 250th birthday. , the United States of America: We The
People. Click Here