CHALK. 



l 59 



w 



heart 

 urchin, V 



balk. 



bedding; occasionally these concretions are con- 

 g ether by tabular flint The flint nod- 



n since 

 the upheaval of the 

 chalk, and they arc 

 a r 

 oped on tl 



he chalk 



has been strained and 



g the 



f the Thames. 



The 



flint which have I 

 n such. 

 sure* the 



so that 



arge on one sid< h a barrier 



and small on the 



When the chalk is examined under the micro- 

 sco: 5 bulk appears to 



• the group 



\ Inch appeared in the 

 :nd survive at the day. The 



mportant of tl >mprise 



the heavy shell, S I something like a nautilus, 



nan tellaria, the broader shell more liki 



Ammonite, named //////<?, the spiral shell 



^1 Bulimina y and the little 

 - formed of spheres, which succeed each 

 other in a dep: • re. The other half of the 



chalk c< - sts "fa multitude of fragments, large- 

 ly formed of the prisms which compose shells 

 mollusca, flakes of the shells of Terebratula and 

 ind minute fragments of corals and 

 Bry and when these organisms cannot be 



