Pliocene.
Miocene.
Eocene. Vertebrate air-population (Bats).
Cretaceous.
Jurassic. Vertebrate air-population (Birds and
Pterodactyles).
Triassic.
Upper Palaeozoic.
Middle Palaeozoic. Vertebrate land-population (Amphibia,
Reptilia [?]).
Lower Palaeozoic.
Silurian. Vertebrate water-population (Fishes).
Invertebrate air and land-
population (Flying Insects and Scorpions).
Cambrian. Invertebrate water-population (much
earlier, if Eozoon is animal).

In the right-hand column I have noted the group of strata in
which, according to our present information, the land,
air, and water populations respectively appear for
the first time; and in consequence of the ambiguity about the
meaning of "fowl," I have separately indicated the first
appearance of bats, birds, flying reptiles, and flying insects.
It will be observed that, if "fowl" means only "bird," or at
most flying vertebrate, then the first certain evidence of the
latter, in the Jurassic epoch, is posterior to the first
appearance of truly terrestrial Amphibia, and possibly of
true reptiles, in the Carboniferous epoch (Middle Palaeozoic) by
a prodigious interval of time.