HORSE, Fossil. Remains of horses, often of extinct species. have been found in the cave-beds, river-gravels. bone-licks, and loess deposits of the Quaternary Period, or 'Age of Man,' in almost all parts of the world. in the more ancient de posits of the Tertiary Period, or 'Age of Mam mals,' have been found remains of a series of ancestors of the horse, which illustrate the evo lution of this race through this entire geological period, a time probably of some millions of years. Fossil horses of the Age of Man are much like the existing species, and are included for the most part in the same genus (Equus). They have been found in Europe, Asia, Africa, North and South America. but none in Australia or in the Oceanic islands, except in those which, like the British Isles, were joined to the continental mainland during the early part of the Quaternary Period. With these exceptions the animal was of world-wide distribution, and inhabited espe cially the open grassy plains and high plateaus of the interior of the great continents, at the be ginning of the Age of Man. All these races were at first wild.
In the New World they became extinct. When the Spaniards first, invaded the two Americas they found no horses, wild or domesticated. The Indians, who had domesticated the llama. the alpaca. and the dog. knew nothing of the horse, and were astonished and terrified at the sight of the strange and unfamiliar animals which the newcomers rode. Yet, when introduced by the white races, the horse ran wild and flourished and increased greatly in the same regions where its native cousins had formerly lived. showing how well the country was suited to their needs. ll'hy the earlier native horses became extinct is a problem not yet solved.
In Central Asia, two wild races, Przewalsky's horse and the Asiatic wild ass, or kiting (q.v.), persist to the present day; others were domesti• eated by man in the earliest times, and their use in Chaldea and Egypt for draught and riding is depicted in the ancient mural paintings. In
Africa the larger species became extinct, hut the smaller zebras still survive in the southern part of the continent, and the African wild as in the northern part (Somaliland).
The wild species of Europe. a small race. short legged and shaggy-haired. was domesticated by man, for it is represented in rude prehistoric drawings scratched on bone or ivory by men of the Neolithic or Polished-Stone Age.
The domesticated horses now in use are chiefly derived from the Asiatic race, but it is probable that in some breeds there is a considerable strain of this European species or variety, and it is possible also that African races may have been domesticated and to some extent mixed with the Asiatic species. The existing wild horses of North and South America, the broncos and mus tangs, are descendants of the animals brought over by the Spaniards; but it is possible that in South America some survivors of the native races still existed at the time of the discovery of the continent, and mixed with the introduced species when it ran wild.
In general, only fragmentary specimens, parts of skulls, hones, or teeth of these extinct horses have been found fossil, so that their characters are very imperfectly known. A number of com plete skeletons were found in Texas in 1899. one of which was placed in the American Museum of Natural History, New York. This species, Equus Sealti, was of the size of a trotting horse, but in proportions more like a zebra, with deep short neck and legs. and small feet. Another extinct species, the Hippiditun of Argentina and Patagonia, was large-headed, with extremely short and stumpy legs and feet, exaggerating some of the peculiarities of the Shetland pony, although of larger size.