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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, Anchitheridæ, 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.

FAMILY 44.–TAPIRIDÆ. (2 Genera? 6 Species.)

GENERAL DISTRIBUTION.

NEOTROPICAL
SUB-REGIONS.

NEARCTIC PALÆARCTIC ETHIOPIAN I ORIENTAL I AUSTRALIAN SUB-REGIONS. SUB-REGIONS. SUB-REGIONS. SUB-REGIONS. SUB-REGIONS.

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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.

Extinct 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 Palæotheridæ, already noticed in chapter vi. (vol. i. pp. 119–125).

FAMILY 45.—RHINOCEROTIDÆ. (1 Genus, 9 Species.)

GENERAL DISTRIBUTION.

NEOTROPICAL NEARCTIC PALÆARCTIC ETHIOPIAN I ORIENTAL | AUSTRALIAN SUB-REGIONS. SUB-REGIONS. SUB-REGIONS. SUB-REGIONS. SUB-REGIONS. SUB-REGIONS.

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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.

Extinct Rhinocerotidæ.—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

only. The hornless Acerotherium is Miocene only, in both countries. Other genera are, Leptodon from Greece, and Hyracodon from Nebraska, both of Miocene age. More than 20 species of extinct rhinoceroses are known, and one has even been found at an altitude of 16,000 feet in Thibet.

FAMILY 46.—HIPPOPOTAMIDÆ. .(1 Genus, 2 Species.)

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The Hippopotamus inhabits all the great rivers of Africa; a distinct species of a smaller size being found on the west coast, and on some of the rivers flowing into Lake Tchad.

Fossil Hippopotami.Eight extinct species of Hippopotamus are known from Europe and India, the former Post-pliocene or Pliocene, the latter of Upper Miocene age. They ranged as far north as the Thames valley. An extinct genus from the Siwalik Hills, Merycopotamus, according to Dr. Falconer connects Hippopotamus with Anthracotherium, an extinct form from the Miocene of Europe, allied to the swine.

FAMILY 47.—SUIDÆ. (5 Genera, 22 Species.)

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The Swine may be divided into three well-marked groups, from peculiarities in their dentition. 1. The Dicotylinæ, or

peccaries (1 genus, Dicotyles). These offer so many structural differences that they are often classed as a separate family. 2. The true swine (3 genera, Sus, Potamochærus, and Babirusa); and, 3. The Phacochærinæ, or wart hogs (1 genus, Phacochorus). These last are also sometimes made into a separate family, but they are hardly so distinct as the Dicotylinæ.

The Peccaries (2 species), are peculiar to the Neotropical region, extending from Mexico to Paraguay. They also spread northwards into Texas, and as far as the Red River of Arkansas, thus just entering the Nearctic region ; but with this exception swine are wholly absent from this region, forming an excellent feature by which to differentiate it from the Palæarctic.

Sus (14 species), ranges over the Palæarctic and Oriental regions and into the first Australian sub-region as far as New Guinea ; but it is absent from the Ethiopian region, or barely enters it on the north-east. Potamochorus (3 species ?), is wholly Ethiopian (Plate V. vol. i. p. 278). Babirusa (1 species), is confined to two islands, Celebes and Bouru, in the first Australian sub-region.

Phacochoerus (2 species), ranges over tropical Africa from Abyssinia to Caffraria.

Dr. J. E. Gray divides true swine (Sus) into 7 genera, but it seems far better to keep them as one.

Fossil Suido.— These are very numerous. Many extinct species of wild hog (Sus), are found in Europe and North India, ranging back from the Post-pliocene to the Upper Miocene formations. In the Miocene of Europe are numerous extinct genera, Bothriodon, Anthracotherium, Palæochorus, Hyotherium, and some others; while in the Upper Eocene occur Cebochorus, Choropotamus, and Acotherium,—these early forms having more resemblance to the peccaries.

None of these genera are found in America, where we have the living genus Dicotyles in the Post-pliocene and Pliocene deposits, both of North and South America ; with a number of extinct genera in the Miocene. The chief of these are, Elotherium, Pera chorus, Leptochorus, and Nunohyus, all from Dakota, and Thinohyus, from Oregon. One extinct genus, Platygonus, closely allied to Dicotyles, is found in the Post-pliocene of Nebraska.

VOL. II.-15

Oregon, and Arkansas. Elotherium is said to be allied to the peccary and hippopotamus. Hyopotamus, from the Miocene of Dakota, is allied to Anthracotherium, and forms with it (according to Dr. Leidy) a distinct family of ancestral swine.

It thus appears, that the swine were almost equally well represented in North America and Europe, during Miocene and Pliocepe times, but by entirely distinct forms; and it is a remarkable fact that these hardy omnivorous animals, should, like the horses, have entirely died out in North America, except a few peccaries which have preserved themselves in the sub-tropical parts and in the southern continent, to which they are comparatively recent emigrants. We can hardly have a more convincing proof of the vast physical changes that have occurred in the North American continent during the Pliocene and Post-pliocene epochs, than the complete extinction of these, along with so many other remarkable types of Mammalia.

According to M. Gaudry, the ancestors of all the swine, with the hippopotami and extinct Anthracotherium, Merycopotamus, and many allied forms, are the Hyracotherium and Pliolophus, both found only in the London clay belonging to the Lower Eocene formation.

FAMILY 48.—CAMELIDÆ. (2 Genera, 6 Species).

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The Camels are an exceedingly restricted group, the majority of the species now existing only in a state of domestication. The genus Camelus (2 species), is a highly characteristic desert form

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