It was with great excitement and not a little pride that Perry came racking up to the camp. He held up the Dorcas gazelle as he approached, and even in the dusk the slender horns could be seen. As soon as he drew near, moreover, he shouted, “Uncle George, I’ve got an Eosiren!” “That’s a gazelle, not an Eosiren,” said the professor, smiling. He had been a little anxious and was unfeignedly glad to see the boy safe, and in good spirits. “I don’t mean this,” said the boy. “What nonsense, Uncle George! No, but really, I did find one!” “Did it bite?” “Please don’t tease,” protested Perry. “Honest, I did!” The leader of the expedition looked inquiringly at the boy’s companion, as the latter dismounted and came up. “He’s right, I think, Dr. Hunt,” responded Antoine, in answer to the look. “I knew we were late and it was getting so dark that I didn’t have much chance to examine it, but it looked to me like _Eosiren Andrewsii_.” “You don’t suppose it was Eotherium?” the professor asked, hopefully. “I’m very anxious to take home to the Museum a good Eotherium. What level was it on?” “On this one, sir,” the younger paleontologist answered, “in the estuarine deposit, not in the Birket-el-Qurun level. That was why I thought immediately it must be Eosiren. There’s not much chance of finding Eotherium as high as this level, is there?” “Very little, I should say; almost none,” was the reply. “Is there such an awful lot of difference, Uncle George?” the boy asked. “That is, between this level and the one underneath. I know, of course, the under one is the oldest, but are the fossils so different?” “Very different, my boy,” was the reply. “They would have to be, for almost a million years passed between the deposits of this level and that. The stratum of which Antoine is speaking, just above the level of Birket-el-Qurun, is a marine limestone. This level is estuarine, that is to say, it is a deposit of material brought down by the great river that flowed through this valley millions of years ago, and like most estuarine deposits, the fossils found in this stratum are of the land as well as of the sea. “You can understand, Perry, that in a true marine or sea deposit you wouldn’t find land animals. It would be as foolish to look for land animals in a marine deposit as it would be to go dredging in the middle of the North Atlantic now for the bones of a modern rhinoceros, or to scour the surface of the western prairies in the hope of finding a modern whale left high and dry.” “So mine isn’t one of the oldest,” said Perry, disappointed. “I’d been hoping I’d found something that nobody had ever seen before.” “You’re greedy,” his uncle said, smiling; “many an old fossil-hunter has worked for years before finding a specimen of a species new to science, and yet you expect to kick one up on the very first day.” “I don’t know that I really expected to, Uncle George,” the lad replied, “but I would like to collar a new one sometime.”