126 



THE STORY OF THE EARTH. 



the upper Oolites of England. These three divi- 

 sions in this country are greatly subdivided by 



differences in min- 

 eral character, as 



well as by fossils. 



The Lias is gen- 

 erally recognised 

 by the great 

 breadth of country 

 that it covers be- 

 tween Whitby and 

 Lyme Regis, by 

 its thickness, and 

 its many sub-divis- 

 ions which are 

 traced through the 

 country. It is. as 

 a rule, a blue-black 

 clay alternating 

 with thin, regular layers of earthy limestone, 

 that the alternations of clay and limestone which 

 characterise the Kinetic beds are continued, with 

 a multitude of repetitions. The bias limestones 

 metimeS a tendency to be brown. The 



thickness of the Lower Lias varies between 500 

 feet at Lyme Regis and Soo feet on the Yorkshire 

 coast. The common bias I Oyster is the Gryphaea 



I ' ISlOnally, in the country towards 



me the bias almost thins away where it n 



the Carboniferous limestone, and it is 



e that the different beds vary in thickn< 



'.v. The marine and terrestrial sauri; 

 d chiefly in the lower beds of the 1 ,< >w 1 



in the south of England. They include both 

 [chtl nirs. Nearer the top 



, . ■ terrest rial ar- 



jDUT\*T«r oavujlsToric 



Map OF an Octi.if.r. 

 Fig. 19. — Map of an outlier of Lias be- 

 tween Market Drayton and Whit- 

 church, proving that the Lias was 

 spread over the \\ I land. 



