Order of Succession of Sedimentary Formations. — Frequent
Unconformability of Strata. — Imperfection of the Record. —
Defectiveness of the Monuments greater in Proportion to their
Antiquity. — Reasons for studying the newer Groups first. —
Nomenclature of Formations. — Detached Tertiary Formations scattered
over Europe. — Value of the Shell-bearing Mollusca in Classification. —
Classification of Tertiary Strata. — Eocene, Miocene, and Pliocene
Terms explained.