The trail of the Loup; being a history of the Loup River region . e various clays, chalks and sandstones, and are rich PHYSICAL FEATURES 23 in finds of fossil leaves and remains of animal life. Thus several hundredspecies of ferns, cycads and conifers have been counted, and some hundredor more reptile forms, ranging in size from twelve to seventy-five feet areknown to have existed. The last great aeon in geological history is now at hand. This is theGenozoic Time, or Era of Modern Life. A higher vegetation makes its ap-pearance and the great reptiles are rapidly giving way to higher species of
The trail of the Loup; being a history of the Loup River region . e various clays, chalks and sandstones, and are rich PHYSICAL FEATURES 23 in finds of fossil leaves and remains of animal life. Thus several hundredspecies of ferns, cycads and conifers have been counted, and some hundredor more reptile forms, ranging in size from twelve to seventy-five feet areknown to have existed. The last great aeon in geological history is now at hand. This is theGenozoic Time, or Era of Modern Life. A higher vegetation makes its ap-pearance and the great reptiles are rapidly giving way to higher species ofanimal life—the mammals. For convenience this aeon is divided into twoages, the Tertiary and the Quaternary. The Tertiary Age embraces three epochs, the Eocene, the Miocene andthe Pliocene. Of these only the latter two are represented in oui! discussion above it will be borne in mind that over the westernpart of the continent the region of marine waters was past. The RockyMountain revolution had left the Great Plains a part of the continent. But. Jurassic Stagosaurus which flourished in Wyoming and Colorado whileNebraska was an inland sea. It measured from 25 to 30 feet in length this plain was yet very near the sea level, the proof of which is found inthe existence of vast lakes of fresh water both east and west of the RockyMountain range. These were not, however, contemporaneous, but succeed-ed one another as the age proceeded. Thus, in Nebraska we find no traceof Eocene lake beds. Conditions were on the other hand quite changedduring Miocene times; for then a freshwater lake covered much of thewestern part of the state, receiving the drainage of the rivers that now havetheir outlet in the Missouri. Into this lake bed were carried broken downmaterials from the Rocky Mountain axis and the Black Hills, and from thehigher lying Juro-Triassic and Cretaceous deposits. Hither, too, weregathered, as in an immense cemetery, remnants of all the vegetable andanimal life
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