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in both jaws. According to Dr. Gray they form seven families and 24 genera; according to Professor Carus, four sub-families and 8 genera, but as these groups appear to be established on quite different principles, and often differ widely from each other, I shall simply enumerate Dr. Gray's genera with their distribution as given in his British Museum Catalogue. Platanista (2 species), long-snouted porpoises, inhabiting the Ganges and Indus; Inia (1 species), a somewhat similar form, inhabiting the upper waters of the Amazonian rivers: Steno (8 species), Indian Ocean, Cape of Good Hope, and West Pacific; Sotalia (1 species), Guiana; Delphinus (10 species), all the oceans; Clymenia (14 species), all the oceans; Delphinapterus (1 species), South Atlantic ; Tursio (7 species), Atlantic and Indian Oceans; Eutropia (2 species), Chili, and Cape of Good Hope; Electra (8 species), all the oceans; Leucopleurus (1 species), North Sea; Lagenorhynchus (1 species), North Sea; Pseudorca (2 species), North Sea, Tasmania; Orcaella (2 species), Ganges; Acanth0delphis (1 species), Brazil; Phocaena (2 species), North Sea; Neomeris (1 species), India; Grampus (3 species), North Sea, Mediterranean, Cape of Good Hope ; Globiocephalus (14 species), all the oceans; Sphaerocephalus (1 species), North Atlantic ; Orca (9 species), Northern and Southern Oceans; Ophysia (1 species), North Pacific ; Beluga (6 species), Arctic Seas, Australia; Pomtoporia (1 species), Monte Video.
Remains of Cetacea are tolerably abundant in Tertiary deposits, both in Europe and North America. In the Lower Pliocene of England, France, and Germany, extinct species of five or six living genera of whales and dolphins have been found; and most of these occur also in the Upper Miocene, along with many others, referred to about a dozen extinct genera.
In the Post-pliocene deposits of Vermont and South Carolina, several extinct species have been found belonging to living genera; but in the Miocene deposits of the Eastern United States cetacean remains are much more abundant, more than 30 species of extinct whales and dolphins having been described, most of them belonging to extinct genera.
The Zeuglodontidae, an extinct family of carnivorous whales, with double-fanged Serrated molar teeth, whose affinities are somewhat doubtful, are found in the older Pliocene of Europe, and in the Miocene and Eocene of the Eastern United States. Zeuglodon abounds in the United States, and one species reached a length of seventy feet. A species of this genus is said to have been found in Malta. Squalodon occurs in Europe and North America; and in the latter country four or five other genera have been described, of which one, Saurocetes, has been found also at Buenos Ayres.
The Sea-cows are herbivorous aquatic animals living on the coasts or in the great rivers of several parts of the globe. Manatus (2 species) inhabits both shores of the Atlantic, one species ranging from the Gulf of Mexico to North Brazil, and ascending the Amazon far into the interior of the continent; while the other is found on the west coast of Africa. Halicore (2 species?), the Dugong, is peculiar to the Indian Ocean, extending from Mozambique to the Red Sea, thence to Western India and Ceylon, the Malay Archipelago and the north coast of Australia. Rytina (1 species), supposed to be now extinct, inhabited recently the North Pacific, between Kamschatka and Behring's Straits.
Fossil Sirenia. Extinct species of Manatus have been found in the Post-pliocene deposits of Eastern North America from Maryland to Florida; and an extinct genus, Prorastomus, in some Tertiary deposits in the Island of Jamaica.
In Post-pliocene deposits in Siberia, remains of Rytina have been found; while several species of the extinct genus Halitherium, perhaps intermediate between Manatus and Halicore, have been found in the older Pliocene and Upper Miocene of France and Germany.
The Horses, Asses, and Zebras form a highly specialized group now oomfined to the Ethiopian and Palaearctic regions, but during the middle and later tertiaries having a very extensive range. The zebras (3 species) inhabit the greater part of the Ethiopian region, while the asses (4 species) are characteristic of the deserts of the Palaearctic region from North Africa and Syria to Western India, Mongolia, and Manchuria. The domestic horse is not known in a wild state, but its remains are found in recent deposits from Britain to the Altai Mountains, so that its disappearance is probably due to human agency.
Extinct Equidae—Extinct forms of this family are very numerous. The genus Equus occurs in Post-pliocene and Pliocene deposits in Europe, North America, and South America. In North America the species are most numerous. An allied genus Hipparion, having rudimentary lateral toes, is represented by several species in the Pliocene of North America, while in Europe it occurs both in the Older Pliocene and Upper Miocene. Various other allied forms, in which the lateral toes are more and more developed, and most of which are now classed in a distinct family, Anchitheridae, range back through the Miocene to the Eocene period. A sufficient account of these has already been given in vol. i. chap. vi. p. 135, to which the reader is referred for the supposed origin and migrations of the horse.
The Tapirs form a small group of animals whose discontinuous distribution plainly indicates their approaching extinction. For a long time only two species were known, the black American, and the white-banded Malay tapir, the former confined to the equatorial forests of South America, the latter to the Malay peninsula, Sumatra, and Borneo (Plate VIII. vol. i. p. 337). Lately however another, or perhaps two distinct species (or according to Dr. J. E. Gray, four ) have been discovered in the Andes of New Granada and Ecuador, at an elevation of from 8,000 to 12,000 feet; while one or perhaps two more, forming the allied genus Elasmognathus, have been found to inhabit Central America from Panama to Guatemala.
Eatinct Tapirs.-True tapirs inhabited Western Europe, from the latest Pliocene back to the earliest Miocene times; while they only occur in either North or South America in the Postpliocene deposits and caves. The singular distribution of the living species is thus explained, since we see that they are an Old World group which only entered the American continent at a comparatively recent epoch. An ancestral form of this group—Lophiodon—is found in Miocene and Eocene deposits of Europe and North America; while a still more ancient form of large size is found in the Lower Eocene of France and England, indicating an immense antiquity for this group of Mammalia. There are many other extinct forms connecting these with the Palaeotheridae, already noticed in chapter vi. (vol. i. pp. 119–125),
Living Rhinoceroses are especially characteristic of Africa, with Northern and Malayan India. Four or perhaps five species, all two-horned, are found in Africa, where they range over the whole country south of the desert to the Cape of Good Hope. In the Oriental region there are also four or five species, which range from the forests at the foot of the Himalayas eastwards through Assam, Chittagong, and Siam, to Sumatra, Borneo and Java. Three of these are one-horned, the others found in Sumatra, and northwards to Pegu and Chittagong, two-horned. The Asiatie differ from the African species in some dental characters, but they are in other respects so much alike that they are not generally considered to form distinct genera. In his latest catalogue however (1873), Dr. Gray has four genera, Rhinoceros (4 species), and Ceratorhinus (2 species), Asiatic; Rhinaster (2 species), and Ceratotherium (2 species), African.
Eatinct Rhinocerotidae.—Numerous species of Rhinoceros ranged over Europe and Asia from the Post-pliocene back to the Upper Miocene period, and in North America during the Pliocene period