discovery of bird-like reptiles and reptilian birds. Compsognathus and Archæopteryx of the Old World, and Ichthyornis and Hesperornis of the New, are the stepping-stones by which the Evolutionist of to-day leads the doubting brother across the shallow remnant of the gulf, once thought impassable."[22] [22] _The Introduction and Succession of Vertebrate Life in America._ An address delivered before the American Association for the Advancement of Science, at Nashville, Tenn., August, 1877. See _Nature_, vol. xvi. We now pass on to describe two of the strangest and most wonderful of all the Dinosaurs, recently discovered in the far West. The first of these is the Stegosaurus,[23] or plated lizard, not wholly unknown before, because part of its skeleton was found some years ago in a brickfield in the Kimmeridge Clay at Swindon. It has been proved that some of the bones to which the name Omosaurus[24] has been applied really belonged to the former genus. [23] Greek--_stegos_, roof or covering; _sauros_, lizard. [24] Greek--_omos_, humerus, and _sauros_, lizard. With such complete specimens now known by Professor Marsh's descriptions, it will not be necessary to mention the meagre remains discovered in this country, or the conclusions arrived at by Owen and Seeley, interesting as they are. In the year 1877 Professor Marsh described, in the _American Journal of Science_, a considerable portion of a skeleton of a Stegosaur, remarking that this genus proved to be one of the most remarkable animals yet discovered. It was found on the eastern flank of the Rocky Mountains, in strata of Jurassic age; they indicated an animal about twenty-five feet long, and for this discovery Science is indebted to Professor A. Lakes and Engineer H. C. Beckwith of the United States Navy, who found the remains in Colorado, near the locality of the gigantic Atlantosaurus. The solid limb-bones seem to point to an aquatic life, but there can be little doubt that the monster did not pass all its time in the water. (Fig. 25 shows the skeleton.)[25] [25] The writer is informed that this skeleton is not yet mounted in the Yale College Museum, but that it will be before long. Our artist has drawn it as if set up, with a man standing by for comparison.