This was the beginning of the †paired-horned rhinoceroses (_†Diceratherium_) which so flourished in the John Day and the lower Miocene. [Illustration: FIG. 135.—†Hornless rhinoceros (_†Cænopus tridactylus_) of the White River stage. Restored from a skeleton in the American Museum.] Of the horses there was no great variety and all the species so far discovered are included in a single genus (_†Mesohippus_), though there was a decided increment in the size of the successive species from the earlier to the later portion of the stage. Looked at superficially, it seems absurd to call these little creatures “horses” at all and the term can be justified only as implying that they were ancestral members of the family. The largest of the White River species hardly exceeded a sheep in size and all of them had comparatively short necks, long and slender legs and three-toed feet. The low-crowned grinding teeth show that they were browsers, not grazers. The abundant Eocene family of the †Lophiodontidæ made its last appearance in the White River, where it was scantily represented by slender, long-legged animals (_†Colodon_), with feet singularly like those of the contemporary horses, except that there were four toes in the front foot. Tapirs (_†Protapirus_) were very much less common than rhinoceroses or horses and were hardly half as large as the existing species of the family and of relatively far more slender form; the development of the proboscis had already begun. Lastly, the presence of the clawed †chalicotheres has been reported from the lower Oligocene of Canada, but the material is too fragmentary for generic reference.