┌Upper,
│Lower, or
└Neocomian Age of Reptiles
and Birds (Earliest
Modern Trees)
Age of
Cycads and
Pines. Jurassic ┌Oolite
└Lias Triassic ┌Upper,
│Middle or
│Muschelkalk.
└Lower. Age of Reptiles
and Birds
(Earliest
Marsupial
Mammals.) PalÆozoic. Permian ┌Upper,
│Upper,
│Middle, or
│Magnesian Limestone,
└Lower. (Earliest true
Reptiles) Age of Acrogens and Gymnodperms. (Earliest Land Plants.) Age of Algæ. Carboniferous ┌Upper Coal-Formation.
│Coal-Formation.
│Carboniferous Limestome.
└Lower Coal-Formation. Devonian ┌Upper.
│Middle.
└Lower. Age of
Amphibians
and fishes. Silurian ┌Upper.
└Lower. Age of
Mollusks
Corals and
Crusyaceans. Siluro
Cambrian
or
Ordovician. ┌Upper.
└Lower. Cambrian. ┌Upper.
│Middle.
└Lower.

Eozoic. Huronian ┌Upper,
│Upper,
└Lower. Age of
Protozoa. (First animal
remains) Indications of
Plants not
determinable aurentian. ┌Upper.
│Middle,
│Lower. or
└Bojian.

---