Page images
PDF
EPUB

northern; while Stenorhynchus and Morunga, with their allies, are mostly southern. The genera admitted by Dr. Gray in his catalogue are as follows:

Callocephalus (3 species), Greenland, North Sea, also the Caspian Sea, and Lakes Aral and Baikal ; Pagom ys (2 species), North Sea, North Pacific, and Japan; Pagophilus (2 species), North Pacific and North Atlantic; Halicyon (1 species), North West coast of America ; Phoca (2 species), North Atlantic and North Pacific, Japan ; Halicharus (1 species), Greenland, North Sea, and Baltic ; Pelagius (2 species), Madeira, Mediterranean, Black Sea; Stenorhynchus (1 species), Antarctic Ocean, Falkland Islands, New Zealand ; Lobodon (1 species), Antarctic Ocean; Leptonyx (1 species), Antarctic Ocean, South Australia, East Patagonia ; Ommatophoca (1 species), Antarctic Ocean ; Morunga (2 species), California, Falkland Islands, Temperate regions of Southern Ocean ; Cystophora (2 species), North Atlantic, Antilles.

Fossil Seals.Remains of living species of seals have been found in Post-tertiary deposits in many parts of Europe and in Algeria, as well as in New Zealand. Pristiphoca occitana is a fossil se al from the Pliocene of Montpellier, while a species of Phoca is said to have been found in the Miocene deposits of the United States.

General Remarks on the Distribution of the Carnivora.

Terrestrial Carnivora.- For the purposes of geographical distribution, the terrestrial and aquatic Carnivora differ too widely to be considered in one view, their areas being limited by barriers of a very different nature. The terrestrial Carnivora form a very extensive and considerably varied group of animals, having, with the doubtful exception of Australia, a world-wide distribution. Yet the range of modification of form is not very great, and the occurrence of three families consisting of but one species each, is an indication of a great amount of recent extinction. One of the most marked features presented by this group is its comparative scarcity in the Neotropical region, only four families being represented there (not counting the Ursidae, which has only one Andean species), and both genera and species are few in number. Even the Procyonida, which are especially South

American, have but two genera and six species in that vast area. We might therefore, from these considerations alone, conclude that Carnivora are a development of the northern hemisphere, and have been introduced into the Neotropical region at a comparatively recent epoch. The claim of the Nearctic region to be kept distinct from the Palæarctic (with which some writers have wished to unite it) is well maintained by its possession of at least six species of Mephitis, or skunk, a group having no close allies in any other region,—and the genera Procyon and Bassaris,-for the latter, ranging from the high lands of Guatemala and Mexico to Texas and California, may be considered a Nearctic rather than a Neotropical form. In the other families, the most marked feature is the total absence of Ursidæ from the Ethiopian region. The great mass of the generic forms of Carnivora, however, are found in the Oriental and Ethiopian regions, which possess all the extensive group of Viverridæ (except a few species in the fourth Palæarctic subregion) and a large number of Felidæ and Mustelidæ.

Aquatic Carnivora.—The aquatic Carnivora present no very marked features of distribution, except their preference for cold and temperate rather than tropical seas. Their nearest approximation to the terrestrial group, is supposed to be that of the Otariidæ to the Ursidæ; but this must be very remote, and the occurrence of both seals and bears in the Miocene period, shows, that until we find some late Secondary or early Tertiary formation rich in Mammalian remains, we are not likely to get at the transition forms indicating the steps by which the aquatic Carnivora were developed. The most interesting special fact of distribution to be noticed, is the occurrence of seals, closely allied to those inhabiting the northern seas, in the Caspian, Lake Aral, and Lake Baikal. In the case of the two first-named localities there is little difficulty, as they are connected with the North Sea by extensive plains of low elevation, so that a depression of less than 500 feet would open a free communication with the ocean. At a comparatively recent epoch, a great gulf of the Arctic ocean must have occupied the valley of the Irtish, and extended to the Caspian Sea; till the elevation of the Kirghiz Steppes cut off the

communication with the ocean, leaving an inland sea with its seals. Lake Baikal, however, offers much greater difficulties; since it is not only a fresh-water lake, but is situated in a mountain district nearly 2,000 feet above the sea level, and entirely separated from the plains by several hundred miles of high land. It is true that such an amount of submergence and elevation is known to have occurred in Europe so recently as during the Glacial period; but Lake Baikal is so surrounded by mountains, that it must at that time have been filled with ice, if at anything like its present elevation. Its emergence from the sea must therefore have taken place since the cold epoch, and this would imply that an enormous extent of Northern Asia has been very recently under water.

We are accustomed to look on Seals as animals which exclusively inhabit salt water; but it is probably from other causes than its saltness that they usually keep to the open sea, and there seems no reason why fresh-water should not suit them quite as well, provided they find in it a sufficiency of food, facilities for rearing their young, and freedom from the attacks of enemies. As already remarked in vol. i. p. 218, Mr, Belt's ingenious hypothesis (founded on personal examination of the Siberian Steppes), that during the Glacial period the northern ice-cap dammed up the waters of the northward flowing Asiatic rivers, and thus formed a vast fresh-water lake which might have risen as high as Lake Baikal, seems to offer the best solution of this curious problem of distribution.

Range of Carnivora in Time.-Carnivora have been found in all the Tertiary deposits, and comprise a number of extinct genera and even families. Several genera of Canidæ occur in the Upper Eocene of Europe; but the most remarkable fact is, that even in the Lower Eocene are found two well-marked forms, Palæonyctis, one of the Viverridæ, and Arctocyon, forming a distinct family type of very generalized characters, but unmistakably a carnivore. This last has been found at La Fère, in the north-east of France, in a deposit which, according to M. Gaudry, is the very lowest of the Lower Eocene formation in Europe. Arctocyon is therefore one of the oldest, if not the very oldest, of the higher forms of mammal yet discovered.

Order V.-CETACEA.

FAMILY 36.–BALÆNIDÆ. (6 Genera, 14 Species.) GENERAL DISTRIBUTION.—Temperate and Cold Seas of both Northern and

Southern Hemispheres.

This family comprises the whalebone or “right " whales, the best known species being the Greenland whale (Balæna mysticetus). Allied species are found in all parts of the southern seas, as far north as the Cape of Good Hope ; while some of the northern species are found off the coast of Spain, and even enter the Mediterranean. As most of the species indicated are imperfectly known, and their classification by no means well settled, no useful purpose will be served by enumerating the genera or sub-genera.

FAMILY 37.–BALÆNOPTERIDÆ. (9 Genera, 22 Species.)

GENERAI. DISTRIBUTION.—Cold and Temperate Seas of both Hemispheres.

This family comprises the finner whales and rorquals, and are characterised by possessing a dorsal fin and having the baleen or whalebone less developed. They are abundant in all northern seas, less so in the southern hemisphere, but they seem occasionally to enter the tropical seas. The best known genera are Megaptera (7 species); Physalus (4 species); and Balænoptera (2 species); all of which have species in the North Sea.

FAMILY 38.–CATODONTIDÆ. (4 Genera, or Sub-Genera,

6 Species.) GENERAL DISTRIBUTION.-All the Tropical Oceans, extending north and south

into Temperate waters.

This family, comprising the cachalots or sperm whales, and black-fish, are separated from the true whales by having teeth in the lower jaw and no whalebone. They are pre-eminently a tropical, as distinguished from the two preceding which are

arctic and antarctic families. The spermaceti whale (Catodon macrocephalus) abounds in the Pacific Ocean and in the deep Moluccan Sea, and also in the Indian Ocean and the Mozambique Channel. In the Atlantic it is scarce, although it occasionally comes north as far as our shores.

The genera of Catodontidæ as given by Dr. Gray are, Catodon (2 species ?), Warm Eastern Oceans; Physeter (1 species), “the black fish,” North Sea; Cogia (2 species), South Temperate Oceans; Euphysetes (1 species), Coast of Australia.

FAMILY 39.-HYPEROODONTIDÆ. (9 Genera or Sub-Genera,

12 Species.)

GENERAL DISTRIBUTION.- Atlantic, Mediterranean, Indian Ocean, and Southern

Ocean.

This family consists of the beaked whales, which have no permanent teeth in the upper jaw. The genera, according to Dr. Gray, are, Hyperoodon (2 species) " bottle-nosed whales,” North Sea; Lagenocetus (1 species), North Sea ; Epiodon (2 species), North and South Atlantic; Petrorhynchus (2 species), Mediterranean Sea and Southern Ocean; Berardius (1 species), New Zealand; Xiphius (1 species) North Atlantic; Dolichodon (1 species), Cape of Good Hope ; Neoziphius (1 species) Mediterranean; Dioplodon (1 species, Indian Ocean.

FAMILY 40.—MONODONTIDÆ. (1 Genus, 1 Species.)

The “Narwhal” (Monodon monoceros) which constitutes this family, is placed by Dr. Gray along with the “white whales," in his family Belugidæ. It inhabits the North Sea.

FAMILY 41.-DELPHINIDÆ. (24 Genera or Sub-Genera,

100 Species.) GENERAL DISTRIBUTION.--All Oceans, Seas, and Great Rivers of the globe.

This family, including the Porpoises, Dolphins, White Whales, &c., may be described as small, fish-shaped whales, having teeth

« EelmineJätka »