The parent stock of our numerous breeds of cattle is not known with absolute certainty ; the nearest approach to British Wild Cattle being a celebrated breed which is still preserved in one or two places. These "Chillingham Cattle" are a fine wild breed, which at one time doubtless existed over a considerable part of Britain. They are pure white, with a black muzzle, the horns white, tipped with black. Though degenerate in point of size, the Chillingham Cattle are probably the descendants of the "mountain-bull" or "Urus," which existed in a wild state in Gaul at the time of Coesar's invasion. The smaller breeds of European Cattle appear to be descended from a now extinct species, the "British Short-horn" (Bos longifrons). Another large Ox, which formerly existed in Britain, and abounded over the whole of Europe, is the Aurochs or Lithuanian Bison (Bos bison). The Aurochs is of very large size, considerably exceeding the common Ox in bulk. It still occurs in the forests of the Caucasus in a wild state, but it no longer occurs wild in Europe, if we except a herd maintained by the Czar in one of the forests of Lithuania.

* In the Merino Sheep, and in some other breeds also, the males only are horned.

Nearly allied to the Aurochs is the American Bison or Buffalo (Bison Americanus). This species formerly occurred in innumerable herds in the prairies of North America, but it has been gradually driven westwards, and has been much reduced in numbers. It has an enormous head, a shaggy mane, and a conical hump between the shoulders. Two other very well known forms are the Cape Buffalo (Bubalus coffer) and the common Buffalo (Bubalus bubalis). The former of these occurs, with two allied forms, in southern and eastern Africa, and the latter is domesticated in India and in many parts of the south of Asia. The horns in both species are of large size, and their bases are confluent, so that the forehead is protected by a bony plate of considerable thickness.

Amongst the more remarkable Asiatic Oxen may be mentioned the Zebu (Bos Indicus) distinguished by the fatty hump over the withers at the back of the neck, and the Yak (Poephagus grunniens) of Thibet, remarkable for its long silky tail, and the possession of a fringe of long hair along its shoulders, flanks, and thighs. The "humped" Cattle of the East are almostly certainly descended from a stock different to that which has given origin to the humpless races. They are known from Egyptian monuments to have been domesticated at an extremely early period ; but their wild form is unknown.

The last of the Oxen which deserves notice is the curious Musk-ox (Ovibos moschatus). This singular animal is at the present day a native of Arctic America, north of latitude 60°, and is remarkable for the great length of the hair. It is called the Musk-ox, because it gives out a musky odour. Like the Reindeer, the Musk-ox had formerly a much wider geographical range than it has at present; the conditions of climate which are necessary for its existence having at that time extended over a very much larger area than at present. The Musk-ox, in fact, in Post-tertiary times is known to have extended over the greater part of Europe, remains of it occurring abundantly in certain of the bone-caves of France. Good authorities regard the Musk-ox as being a sheep, and therefore truly referable to the Ovidae.

As regards the distribution of the Ungulata in time, the order is not known to have commenced its existence earlier than the Eocene Tertiary; but it presented itself throughout the whole Tertiary period under such numerous and such varied types that it will not be possible in this place to do more than simply indicate the geological range of the principal families.

Of the Rhinocerotidae, hornless forms (Acerotherium) occur in Miocene and Pliocene strata; but the best-known fossil species is the two-horned Woolly Rhinoceros (R. tichorhinus). This curious species occurs in Post-pliocene deposits, and must have ranged over the greater part of Europe. It was adapted to a temperate climate, and, like the Mammoth, possessed a thick covering of mixed wool and hair. This has been demonstrated by the discovery of a frozen carcass in Siberia. The curious genus Diceratherium, with its transverse pairs of horns, is from the Miocene of North America.

The Tapiridae are represented in the Eocene and Miocene by the genus Lophiodon. (Coryphodon, which has generally been placed here, has been shown by Marsh to have five toes to both feet, and it, therefore, forms the type of a special family of Perissodactyles.) The genus Tapirus itself begins in the Miocene.

The Brontotheridae. are wholly extinct, and are confined to the Miocene of North America.

The Palaeotheridae are likewise completely extinct, and are confined to the Eocene and Miocene.

The Macrauchenidae are confined to the Pliocene and Post-pliocene of South America.

The distribution of the Equidae in time has already been spoken of (see p. 702). The oldest genus of the family is the Eohippus of the American Eocene.

Amongst the Artiodactyles, the earliest representative of the Hippopotamidae. is the Hexaprotodon of the Upper Miocene (Pliocene?) of India, which differs from Hippopotamus proper only in having six lower incisors, in place of four. The latter genus appears in Europe in the Pliocene.

A very large number of fossil forms of Snida are known from the Tertiaries of both the Old and New Worlds, beginning in the Eocene (Chaeropotamus, etc.)

The Oreodontidae. are wholly confined to North America, and belong to the Miocene and Pliocene.

The Anoplotheridae are wholly extinct, and are confined to the Eocene and Miocene periods.

The Camelidae are first represented in the Miocene deposits of North America (Poebrotherium, etc.), and the later Tertiaries and Post-tertiaries of the same country have yielded several other extinct types of this family. Fossil remains of Camelidae also occur in the Upper Miocene (Pliocene?) of India; and early types of the Llamas occur in the Pliocene of South America.

The Tragnlidae are first known to have come into existence during the Miocene period (Amphitragulus and Dremotheriiim): but it is possible that some Eocene types (Xiphodon and Caino-therium) are really referable here.

The Cervidae appear for the first time in the Miocene (Dorca-therium, Dicrocerus, etc.) Cervus itself appears in the Upper Miocene, and of the same age is the genus Amphimoschus, related to the living Musk-deer.

The first representative of the Camelopardalidae, so far as known, is the Helladotherium of the Upper Miocene of France, Greece, and India.

The Antilopidae appear in forms closely allied to recent ones in the Miocene of Europe; and in beds of Upper Miocene (Pliocene ?) age in India we have the aberrant four-horned types which constitute the genera Sivatherium and Bramatherium.

True Bovidae occur in the Miocene (Pliocene?) of India, and the Pliocene of Europe, whilst Ovidae. resembling existing types are not known from deposits earlier than the Post-pliocene.