CHAPTER XXI.

The Post-Pliocene period--Division of the Quaternary deposits into
Post-Pliocene and Recent--Relations of the Post-Pliocene deposits
of the northern hemisphere to the "Glacial period"--Pre-Glacial
deposits--Glacial deposits--Arctic Mollusca in Glacial
beds--Post-Glacial deposits--Nature and mode of formation of
high-level and low-level gravels--Nature and mode of formation
of cavern-deposits--Kent's Cavern-Post--Pliocene deposits of
the southern hemisphere.

CHAPTER XXII.

Life of the Post-Pliocene period--Effect of the coming on and
departure of the Glacial period upon the animals inhabiting the
northern hemisphere--Birds of the Post-Pliocene--Mammalia of the
Post-Pliocene--Climate of the Post-Glacial period as deduced from
the Post-Glacial Mammals--Occurrence of the bones and implements
of Man in Post-Pliocene deposits in association with the remains
of extinct Mammalia--Literature relating to the Post-Pliocene
period.

CHAPTER XXIII.

The succession of life upon the globe--Gradual and successive
introduction of life-forms--What is meant by "lower" and "higher"
groups of animals and plants--Succession in time of the great
groups of animals in the main corresponding with their zoological
order--Identical phenomena in the vegetable kingdom--Persistent