Next day, with his uncle, the boy started north for the Grey Bull River country to review the Lower Eocene Beds. Perry thought he knew his geology fairly well, but he had not the slightest idea that there could be as much excitement in a mere ride through that country with some one who was as expert as the professor. The finding of each new rock was like the finding of a new wild animal, and Perry aptly described the ride as “gunning for strata!” The trip through the Puerco and Torrejon regions of New Mexico was also a delight to the boy, but as their researches took them further and further down the rock levels and they grew nearer and nearer to the level where the giant reptiles could be found, all the great wonder revived, and at night, in his tent, Perry dreamed again and again that he was on the back of the unicorn, speeding through that Jurassic world of giant dinosaurs. At last, the New Mexico strata sufficiently studied, the two took the train back for Wyoming once more. They picked up their ponies at the nearest station to the reptile beds and a little later stopped at an abandoned sod cabin that had been used by the Museum expedition several years before when taking out specimens from the Bone Cabin quarry. “There, Perry,” said the professor, pointing to the ruins of a small building on a hillock at the end of the valley not far from the sod cabin, “is the most marvelous fossil spot in the world. It is famous to every scientist and will be famous forever.” [Illustration: _Courtesy of American Museum of Natural History._ THE DRYPTOSAURUS, A GIANT CARNIVOROUS REPTILE. This form is closely allied to the Tyrannosaurus, of which several fine skeletons were discovered by the Museum expeditions. The pose of the restoration is a little too agile for a reptilian combat.] “Why, Uncle George?” “That is Bone Cabin Hill, right at the end of that ‘draw,’” was the reply, “and it is the site of the greatest find of dinosaurs made in a single locality in any part of the world. One of our own Museum men made the discovery, in the spring of 1897. “We had been steadily working down all the beds that hold the fossils of mammals, the beds that you and I have seen, Perry, and in the spring of 1897, the Museum decided to undertake the exploration of the rocks that lay below them, rocks of the Cretaceous and Jurassic Periods. We were especially anxious to explore the rocks of the upper Jurassic, which showed the first dawn of the Mammal Age and so we made our way here, to the Laramie Plains, but over towards the base of the famous Como Bluffs. “Marsh and Cope, the great pioneers of all American fossil work, had explored these bluffs thoroughly, so that we were not very sanguine of success.” “Still, Uncle George,” the boy suggested, “weathering is always going on.”