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648 of Iguanodon and Megalosaurus of the Old World—Mosasaurus, and many others. Hadrosaurus was herbivorous, while Lœlaps was a carnivore. Both were biped, terrestrial reptiles, thirty feet long, standing fifteen to twenty feet high, and of very peculiar and interesting structure. The former will be remembered as that of which the spirited restoration, made by Prof. Hawkins for the Central Park, was destroyed by the order of Judge Hilton. Mosasaurus was a snake-like, marine lizard, some sixty or seventy feet long, and of pronounced carnivorous habits. These, with their associates, probably densely populated the land and sea, while the air was the special domain of the huge flying dragons—the pterodactyls. With such a numerous and so enterprising a population, it is evident that life in this time and region was full of variety.

At the close of the Cretaceous age the animal life, both sea and land, was again revolutionized, but by causes which we cannot yet fully understand, as the physical conditions remain nearly the same, and the flora suffered little change. The facts, however, are unquestionable. All the great reptilian fauna disappeared as if by magic, and gave place to herds of mammals, numerous and large it is true, but far inferior in size and armament to their predecessors. In the sea, the whole Ammonite family disappeared at once, and other great changes took place, so that in the upper or Tertiary bed of green-sand, deposited in the same place and under nearly the same conditions as the lower and Cretaceous two, but we know not how many thousands of years after, not a single one of all the species of Cretaceous mollusks, radiates, or marine vertebrates, mingled its remains with those of the new-comers.

—The excavation of New York Harbor and the trough of the Hudson seems to have been effected in late Tertiary times. During the first portion of the Tertiary age—the Eocene—the coast from New York southward was low, and the sea washed the base of the Alleghany Mountains, covering the coast-plain and depositing upon it the uppermost and most recent of the marl-beds of New Jersey. But in the middle and later Tertiary epochs—the Miocene and Pliocene—all the northern portion of the continent stood higher above the sea than now, for we find there no marine deposits of that age; and the immense numbers of fiords, or submerged valleys which fringe the coast, are, as Dana long since pointed out, the results of subaërial erosion and proofs of elevation. A genial climate then prevailed to the Arctic Sea, and all the continent was covered with a more luxuriant flora, and inhabited by a more varied fauna, than can now be found anywhere on its surface.

This was, indeed, for America, the golden age of animals and plants, and in all respects but one—the absence of man—the country was more interesting and picturesque than now. We must imagine, therefore, that the hills and valleys about the present site of New York were