What is of or pertaining to a division of the Silurian formation, corresponding in general to the Lower Silurian of most authors, exclusive of the Cambrian. -- n. The Ordovician formation called?

ordovician — Of or pertaining to a division of the Silurian formation, corresponding in general to the Lower Silurian of most authors, exclusive of the Cambrian. -- n. The Ordovician formation. (Webster's 1913.)

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