Page:Popular Science Monthly Volume 16.djvu/397

 Cystidea, and Edrioasterida; and the Crustaceans by the Eurypterida and Trilobita. Among the vertebrates, no extinct order of fossil fishes has yet been found; but the amphibians have been enlarged by the important order Labyrinthodonta, The greatest additions have been among the reptiles, where the majority of the orders are extinct. Here we have at the present date the Ichthyosauria, Sauranodontia, Plesiosauria, and Mosasauria, among the marine forms; the Pterosauria, including the Pteranodontia, containing the flying forms; and the Dinosauria, including the Sauropoda—the giants among reptiles; likewise the Dicynodontia, and probably the Theriodontia, among the terrestrial forms. Although but few fossil birds have been found below the Tertiary, we have already among the Mesozoic forms three new orders: the Saururæ, represented by Archæopteryx; the Odontotormæ, with Ichthyornis as the type; and the Odontoleæ, based upon Hesperornis; all of these orders being included in the sub-class Odontornithes, or toothed birds. Among mammals, the new groups regarded as orders are the Toxodontia and the Dinocerata, among the Ungulates; and the Tillodontia, including strange Eocene mammals whose exact affinities are yet to be determined.

Among the important results in vertebrate paleontology, are the genealogies, made out with considerable probability, for various existing animals. Many of the larger mammals have been traced back through allied forms in a closely connected series to early Tertiary times. In several cases the series are so complete that there can be little doubt that the line of descent has been established. The evolution of the horse, for example, is to-day demonstrated by the specimens now known. The demonstration in one case stands for all. The evidence in favor of the genealogy of the horse now rests on the same foundation as the proof that any fossil bone once formed part of the skeleton of a living animal. A special creation of a single bone is as probable as the special creation of a single species. The method of the paleontologist in the investigation of the one is the method for the other. The only choice lies between natural derivation and supernatural creation.

For such reasons it is now regarded among the active workers in science as a waste of time to discuss the truth of evolution. The battle on this point has been fought and won.

The geographical distribution of animals and plants, as well as their migrations, has received much new light from paleontology. The fossils found in some natural divisions of the earth are related so closely to the forms now living there, that a genetic connection between them can hardly be doubted. The extinct Marsupials of Australia and the Edentates of South America are well-known examples. The Pliocene hippopotami of Asia and the south of