CHAPTER XXI 

 THE CHALK PERIOD 



ONCE again the European continent and with it Great 

 Britain began to sink. Great Britain at the begin- 

 ning 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 Igiianodan, 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 Iguaiwdon 

 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 Geo- 

 logical 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 



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