How did the ancient reptile aristocracy perish? We are ignorant of the details of the catastrophe, but their final disappearance and replacement by the more modern fauna was connected with a great continental subsidence in the Cretaceous age, and with changes of climate and conditions preceding and subsequent to it. Yet the struggle for continued dominion was hard and protracted; and toward its close some of the champions of the reign of reptiles were the greatest and most magnificent examples of the type; as if they had risen in their might to defy approaching ruin. Thus some of the most stupendous forms appear in the later Cretaceous, after the great subsidence had made progress and almost attained its consummation. Like the antediluvian giants, they were undismayed even when the land began to sink beneath their feet; and for them there was no ark of deliverance. [Illustration: LOWER CRETACEOUS LEAVES. REDUCED IN SIZE.—After Lesquereux. _a_, _Aralia Saporteana_. _b_, _Sassafras araliopsis_. _c_, _Quercus primordialis_. _d_, _Fagus polyclada_. _e_, _Salix proteæfolia_. _f_, _Laurus proteæfolia_.] CHAPTER VIII. THE FIRST FORESTS OF MODERN TYPE. For a long time it was believed by geologists that a great and mysterious gap separated the Upper Cretaceous from the oldest Tertiary formations; and in Western Europe, in so far as physical conditions and animal life are concerned, the severance seemed nearly complete. Oceanic deposits, like the Upper Chalk, are succeeded by beds of littoral and estuarine characters. The last and some of the greatest of the Mesozoic Saurians have their burial-places in the Upper Cretaceous, and appear no more on earth. The wonderful shell-fishes of the Ammonite group, and the cuttle-fishes of the Belemnite type, share the same fate. With the earliest deposits of the Eocene Tertiary came in multitudes of large Mammalia heretofore unknown, and the Cetaceans appear in the sea instead of the great marine lizards; while shells, corals, and crustaceans of modern types swarm in the waters. Thus it is true that a great and apparently somewhat abrupt change takes place at the close of the Cretaceous, and terminates for ever the reptilian age. Even in regions like Western America, where physically the later Cretaceous shades gradually into the earlier Tertiary, so that there have been doubts as to the limits of these several periods, the same great change in animal life occurs.