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Some Early Mammals and the Story of the Horse: Marsh

We pass on to consider the true fossil horses, as worked out by Professors Huxley and Marsh, and others. The modern horse, and that which was known to man in the days before history was written, we may regard as a product of the latest geological period-the Pleistocene. The development of the horse from a primitive five-toed ancestor seems to have taken place along two separate lines, one in Europe and one in America. The latter is the most complete; for it so happens in that country the physical conditions which prevailed throughout nearly the whole of the Tertiary Era were singularly favourable to the preservation of the skeletons of those creatures which lived on land. The various members of the horse tribe that roamed over North America all through these long ages of the past were specially numerous in what is now the Rocky Mountain region, and their remains are sealed up in the strata of these regions. Here in Wyoming and Utah is found one of the oldest direct ancestors of the horse, the Orohippus of Marsh. During the middle Tertiary, or Miocene period, two other lakes existed on either side of the great Eocene basin. The largest of these, to the east of the Rocky Mountains, extended over portions of what are now Dakota, Nebraska, and Colorado. The clays deposited in this lake form the "Bad Lands" of that region, so well known for their fossil treasures. The other Miocene lake was west of the Blue Mountains, where eastern Oregon now is, but, having since been overflowed by a vast sheet of basalt, its thickness is unknown. In this basin the Miohippus of Marsh first makes its appearance.