Page:Evolution of Life (Henry Cadwalader Chapman, 1873).djvu/149

Rh Morning being, was discovered, so called from representing the very simple beings which first appeared on our continent during the dawn of life. The term Azoic is still retained by Geologists as meaning a scarcity of life, not implying, as formerly, entire absence of it. Continuing his journey, our Geologist soon reaches the Potsdam Sandstone, abounding in characteristic fossils, of which the Brachiopod shells and Trilobites, extinct Crustaceans, are very common. Passing by the town of Oriskany, he comes to what is known as the Schoharie Grit, in which the remains of fishes are first found. Finally, he reaches Pennsylvania, abounding in coal, with its ferns and traces of reptiles. If he goes over to New Jersey, he finds in the chalks the reptiles more abundant. To see the higher forms of life in profusion, he must turn to the West, Nebraska and Dakota having furnished the remains of deer, rhinoceros, hyena, lion, etc. The rocks of Canada and New York are the successive beaches left dry by a retreating ocean. This is very evident from the manner in which the rocks follow each other, the ripple-marks still visible on them, and their marine remains. The animals and plants found in the rocks of New York and Pennsylvania, from bearing the stamp of age, are called Paleozoic, or old beings, and the age in which they lived is known as the Primary. The fossils of New Jersey, though still old, are more modern in their appearance than those of New York; they are called, therefore, Mesozoic, or middle-aged beings; the rock containing them forming, with some others not well represented on our continent, the Secondary Age. The Cenozoic, or recent beings, those of Nebraska, for example, lived during the Tertiary Age. Not only are the fossils invaluable to the Zoologist and Botanist, as representing the life of the past, but they are equally important to the Geologist, as we have just seen; his classification of the rocks is principally based on the extinct remains which they contain. The