“ The faunal aspect of the Tertiary periods differs strikingly from that of preceding Secondary or Mesozoic; in place of the great saurian reptiles we find the rapid development and finally the maximum expansion of mammals. Snakes and true birds advanced rapidly towards their modern position. ”

“ Subsequent investigations naturally modified the numerical values upon which this nomenclature was based, but without altering the order of the periods. Later, E. Beyrich introduced the Oligocene period, and some geologists recognize a Palaeocene or early Eocene period. European geologists very generally use the grouping adopted by R. Hörnes:—
Younger Tertiary = Neogene (Miocene, Pliocene) . ”