fossil specimens showed. There are two sets of feathers forming the wings, and the thighs were also covered with feathers. CHAPTER XXI THE CHALK PERIOD Once again the European continent and with it Great Britain began to sink. Great Britain at the beginning of the era which followed the Jurassic system, was joined to France, but south of this barrier was a great fresh-water lake, into which rivers and streams poured from the north and the east. Great forests grew on its borders, forests still crowded with ferns and cycads as in previous ages, but affording scope for pine trees to grow as well. On its borders flourished the giant _Iguanodon_, a great lizard-like animal which could raise itself on its hind legs and lift a fifteen-foot body so as to feed on the branches of the trees. The _Iguanodon_ is a specially interesting fossil reptile, because it was one of the first to be discovered. The first bones and teeth of the Iguanodon were found seventy years ago by a celebrated and most delightful explorer of the earth's crust, Dr. Gideon Mantell, in the strata known as the Wealden, in Sussex, just below the chalk. Dr. Mantell was only a country practitioner, and when he first produced before the Geological Society his _Iguanodon_ remains, and suggested that they were those of a reptile, some doubt was thrown on this conclusion, because geologists believed from the appearance of the teeth that the animal must be of some other animal family. But Dr. Mantell found that a little lizard living in South America had teeth like those he had discovered in his reptile remains, and he persisted in his view. Many years later a wonderful find was made near Brussels in a coal mine near Bernissart, the skeletons of no fewer than twenty-two huge _Iguanodons_ were found complete and embedded in a fairly soft clay-like rock. The authorities of the Government Museum took charge of the place and most carefully removed the skeletons to Brussels, where the complete skeletons of seven were with enormous difficulty and care removed bit by bit from the rock and set up as entire skeletons in the Brussels Museum, where they may be seen. A replica of one of them is at South Kensington. The fore feet of the _Iguanodon_ had five fingers, but the hind foot was very much like that of a bird, and had only three toes, and the bones of the pelvis or hip girdle were extraordinarily like those of a bird. When Professor Huxley examined the first fragments of the _Iguanodon's_ remains he was inclined to believe them to be those of a gigantic bird; and it is generally believed now that it is from this extraordinary reptile stock that the birds were derived.