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).
| General Distribution. | |||||
 | |||||
| Neotropical Sub-regions. | Nearctic Sub-regions. | Palæarctic Sub-regions. | Ethiopian Sub-regions. | Oriental Sub-regions. | Australian Sub-regions. |
| Living Species. | |||||
| 1. — — — | — — — — | — 2. 3 — | — — — — | — — — — | — — — — |
| Extinct Species. | |||||
| 1. — — — | — 2. 3. 4 | — — 3 — | — — — — | — — 3. — | — — — — |
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 of the Palæarctic region, from the Sahara to Mongolia as far as Lake Baikal. Auchenia (4 species), comprehending the Llamas and Alpacas, is equally characteristic of the mountains and deserts of the southern part of South America. Two species entirely domesticated inhabit the Peruvian and Bolivian Andes; and two others are found in a wild state, the vicuna in the Andes of Peru and Chili (Plate XVI. vol. ii. p. [40]), and the guanaco over the plains of Patagonia and Tierra del Fuego.
Extinct Camelidæ.—No fossil remains of camels have been found in Europe, but one occurs in the deposits of the Siwalik Hills, usually classed as Upper Miocene, but which some naturalists think are more likely of Older Pliocene age. Merycotherium, teeth of which have been found in the Siberian drift, is supposed to belong to this family.
In North America, where no representative of the family now exists, the camel-tribe were once abundant. In the Post-pliocene deposits of California an Auchenia has been found, and in those of Kansas one of the extinct genus Procamelus. In the Pliocene period, this genus, which was closely allied to the living camels, abounded, six or seven species having been described from Nebraska and Texas, together with an allied form Homocamelus. In the Miocene period different genera appear,—Pœbrotherium, and Protomeryx,—while a Procamelus has been found in deposits of this age in Virginia.
In South America a species of Auchenia has been found in the caves of Brazil, and others in the Pliocene deposits of the pampas, together with two extinct genera, Palæolama and Camelotherium.
We thus find the ancestors of the Camelidæ in a region where they do not now exist, but which is situated so that the now widely separated living forms could easily have been derived from it. This case offers a remarkable example of the light thrown by palæontology on the distribution of living animals; and it is a warning against the too common practice of assuming the direct land connection of remote continents, in order to explain similar instances of discontinuous distribution to that of the present family.
Family 49.—TRAGULIDÆ. (2 Genera, 6 Species.)
| General Distribution. | |||||
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| Neotropical Sub-regions. | Nearctic Sub-regions. | Palæarctic Sub-regions. | Ethiopian Sub-regions. | Oriental Sub-regions. | Australian Sub-regions. |
| — — — — | — — — — | — — — — | — 2 — — | 1. 2. 3. 4 | — — — — |