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13. What is meant by the denudation of the Weald? How may the removal of the strata which once extended over that area, between the North and South Downs, be accounted for?

14. Why are land-plants and other terrestrial productions, as a general rule, found more frequently in arenaceous and argillaceous, than in calcareous rocks?

15. Name the geological groups of which the following fossils are considered characteristic :-Nucleolites clunicularis, Avicula contorta, Ostrea deltoidea, Pentamerus Knightii, Ammonites serpentinus, Terebratula sella, Voluta Lamberti, Avicula echinata, Scaphites equalis, Lina gigantea, Exogyra virgula, Trilobites, Nummulites.

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