Cenozoic

The whole history of the earth is divided into five eras, with corresponding rock-systems. These are: 1. Archæan or Eozoic¹ era, embodied in the Laurentian system; 2. Palæozoic² era, embodied in the Palæozoic or Primary system; 3. Mesozoic³ era, recorded in the Secondary system; 4. Cenozoic,⁴ recorded in the Tertiary and Quaternary systems; and, 5. The Psychozoic era, or era of Mind, recorded in the recent system.