Chapter XVIII

), a great series of fresh-water beds, 1000 feet in thickness, resting upon marine formations and again covered by other rocks, such as the Cretaceous, more than 1000 feet thick, and of deep-sea origin, we shall find it necessary to seek for a different explanation of the phenomena.

[1] See Woodward’s Manual of Mollusca, 1856.

[2] The fresh-water Mulleria, when young, forms a single exception to the rule, as it then has two muscular impressions, but it has only one in the adult state.

[3] For figures of fossil species of Purbeck, see Chapter XIX [4] See Principles, Index, “Lym-Fiord.”

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