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112 exceedingly complex dentition, arranged in magazines, containing in some instances as many as two thousand teeth. A new group of saurians and several batrachians were also discovered. Explorations were begun in the Jurassic beds of the upper Arkansas River, in 1877, which yielded some of the largest crocodilians known. Other expeditions were sent out into the Permian regions of Texas and into Montana and Nebraska. In the latter he discovered a new geological horizon between White River (lower) and Loup Fork (upper) Miocene, from which several species of peculiar character were obtained. Two expeditions to explore the Loup Fork beds of Kansas obtained numerous reptiles, and mammals, including horses, camels, a new mastodon, and two new rhinoceroses. Explorations in Oregon were begun by parties sent out in 1877, and Professor Cope visited the field in 1879, partly to examine the material that had been collected, among which he found many fine specimens, and partly to study the Pliocene deposit of that region, which was found remarkable for the prodigious number of the bones of birds it contained and for the occurrence of flint implements. In all of these expeditions six hundred and thirty-five new species were discovered, including one hundred fishes, one hundred and seventy-five reptiles, ten birds, and three hundred and fifty mammals, from which have been constituted the extinct orders Actinochiri (fishes), Stegocephali (batrachians), Charistodera, Pythonomorpha, and Theromorpha (reptiles), Tæniodonta, Credonta, and Amblypoda (mammals).

Professor Cope has also contributed to the definite determination of the relative ages of the horizons of the interior of the continent as named by American geologists, and to their reference to corresponding horizons on the European scale, beginning with the Permian and including the Niobrara and Laramie Cretaceous, the Wahsatch, Bridger, White River, Truckee, Loup Fork, and Pliocene Tertiary formations.

The scientific writings of Professor Cope are quite voluminous, and mainly technical in character. They relate to a variety of departments of natural history. The full list of them includes nearly three hundred titles of papers which have been published in the official reports of the Government surveys, the proceedings of the Philadelphia Academy of Sciences, of the American Philosophical Society, the American Association for the Advancement of Science, in the "American Journal of Science and Arts," the "American Naturalist," the "Penn Monthly," and through other channels. By far the largest number of these papers relate to the reptiles and fishes discovered in the different geological formations, extending from the Atlantic coast to the Rocky Mountains, in the surveys of which he has participated. Probably the next largest number concern the cetaceans and mammalia of those formations. About a dozen of them relate to the reptiles and fishes of tropical America; half as many embody studies of the fauna, living and fossil, of caves. Many papers describe living reptiles and fishes. More