THE CHALK PERIOD 



attributed to sea serpents. These reptiles, known as 

 Dolichosaurs, were long-necked, lizard-like reptiles in the 

 beginning of their career, and grew longer and longer 

 in succeeding generations, till at last their descendants 

 were so long and snaky that geologists have called the 

 later specimens "serpents."" These sea serpents were from 

 fifteen to forty-five feet in length, and their remains have 

 been found in the valley of the Meuse. They do not 

 seem to have had a very long career, for they do not 

 appear after the Chalk Age, and no direct descendants 

 are known ; but while they lived they ranged from North 

 and South America to Europe and New Zealand. 



The first true sea turtles appeared and lived and 

 extended their families in great variety. They had 

 broad flat forms, their shells only just covering their 

 ribs like a short Eton jacket ; but they were very large. 

 The greatest of them, Archelon, had a skull larger than 

 that of a horse, and must have measured fully twelve 

 feet across the shell. 



We may consider the birds at the same time as the 

 sea animals or sea reptiles, since they, perhaps, were 

 relations. Moreover, while the birds of Jurassic times 

 were land birds, those of the Chalk period were aquatic. 

 These birds belonged to two widely different classes, one 

 consisting of large birds which did not fly, the other of 

 small birds with great strength of wing and great powers 

 of flight. Of the first kind was the Hesperornis. This 

 was a large flightless bird, specially adapted to diving. 

 Its wings hardly existed, for they had only one bone left ; 

 and that implies the passage of a very long flight of time, 



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