Paleotherium (Fig. 151) and Anoplotherium (Fig. 152), living during the early part of this age, are extremely interesting, being regarded as the progenitors of the odd- and equal-toed Mammalia. The conclusions of Cuvier as to the nature of the Paleotherium, based only on fragmentary remains, were perfectly confirmed by the discovery of an almost entire skeleton. Since that time many allied forms have been described, principally by Prof. Owen, some of which, uniting the Rhinoceros, Tapir, and Horse, make the group of odd-toed, while others, associated with the Hog, Hippopotamus, etc., form that of the equal-toed. Prof. Leidy has described many kinds of horses found fossil in the western part of the United States, etc. (these discoveries are confirmed by those of Owen and Rutimeyer), which represent the transient stages through which the modern horse passes, so that the descent of the Horse from some paleotheroid form is completely made out. As regards the Flora of the Tertiary Age, as compared with that of the Cretaceous and Modern periods, according to Brown, the Apetalae (Fig. 133) were greatly in excess during the Cretaceous period, the Diapetalae were represented by a few species, while the Gamopetalse (Fig. 151) had not appeared. In the Tertiary. Age the Diapetalae exceed the Apetalae, the Gamopetalas being comparatively well represented; while at the present day the great number of Gamopetalous genera seems to indicate that this order of plants is increasing most rapidly. These facts are very significant when compared with what is said of the structure of these plants. The age following the Tertiary, that in which we live, is known as the Age of Man, whose early condition, etc. will be treated of in the chapter on Anthropology. Repeating that great caution must be exercised in accepting the generalization of Geologists as to the relative and absolute age of rocks, a résumé of their fossil remains seems to exhibit the following
