142 THE STORY OF THE EARTH. 



CHAPTER XVII. 



NEOCOMIAN. 



The Neocomian period of ideological time is 

 completely represented in Great Britain in the 



•ton clay, which is about 300 feet thick, and 



to the north of Flambo rough Head. The 



basement bed of this deposit is the Coprolite 



bed which divides it from the Kimeridge clay 

 on which the Speeton clay rests. That bed is a 

 layer of nodules of phosphate of lime, which ap- 

 parently were formed about fossils, like similar 

 beds of phosphate of lime in newer deposits in 



Bedfordshire and Suffolk. This layer of phos- 

 phates marks a change in the life; so that the 

 shells which characterise the Kimeridge clay be- 

 low do not pass above it. It was formerly sup- 

 ed to occur at the top of the Portland beds, 



but tiie Ammonites regarded as Portlandian oc- 

 cur above this junction bed. 



T - re is therefore some ground for regarding 



the Speeton clay above the Coprolite bed 



representing in unbroken marine sequence the 



- which in the south of Engl 



partly lacustrine, partly terrestrial, and partly 



lie, and known as the Portland beds, tin* Pur- 

 .d the Wealden beds, and the bower (ireen- 



• lowest division of the Speeton ckr 

 '. 11 ;i- the zoi,< The 



1 -und in the ( 'oprolite ! 

 • v of tie .' appears some- 



what higher up. The next division is the /one of 

 mniUs jaculum y which ranges through al 



