470 



MESOZOIC ERA— AGE OF REPTILES. 



of this part is all now covered by sea. From New Jersey southward 

 the shore-line was then farther in or west than now. From Maryland 

 to Georgia the shore-line, though farther in than now, was farther out 

 than during the Tertiary, as the Cretaceous is covered by the later de- 

 posits. The Gulf was much more extended both northward and west- 

 ward than either now or in Tertiary times, its shore-line being along 

 the extreme limit of the Cretaceous of this region. From the Gulf 

 there extended northwestward an immensely ivide sea, covering the 

 Plains region and the Kocky Mountain region as far westward as the 

 Wahsatch Eange, and dividing the continent into two continents, an 

 eastern or Appalachian, and a western or Basin region continent. The 

 place of the Wahsatch range was then the marginal bottom of this in- 

 terior Cretaceous sea. The Pacific Ocean at that time washed against 

 the foot-hills of the Sierra Eange, the place of the Coast Eange being 

 thus its marginal bottom. These facts are represented in the accom- 

 panying map. The probable connection of the Gulf with the Pacific 

 is also indicated. 



Fig. 755.— Map of North America in Cretaceous Times. 



Rocks. — The rocks of the Cretaceous period consist of sands, and 

 clays, and limestones, as in other periods, but, as a whole, are less fre- 

 quently metamorphic than in the older rocks. There is, however, one 

 kind of rock found in this age in Europe which is so peculiar and so 

 interesting that it must not be passed over in silence. We refer to the 

 white chalk of England and France, from which the formation and the 

 period take their name, " Cretaceous.'''' 



Chalk. — Chalk is a soft, ivhite, pure carbonate of lime. Scattered 



