THE NEOZOIC AGES. 



243 



leave here to present to the reader a little illustration 

 of the limestone-making Foraminifera of the Creta- 



rOBAMIinrERAL E0CK-BUILDBB8. 



A. Nummulites laevigata— Eocene. 



B. The same, showing chambered interior. 



C. Milioline limestone, magnified — Eocene, Paris. 



D. Hard Chalk, section magnified— Cretaceous. 



ceons and Eocene seas. In the middle above is a 

 nummulite of the natural size. Below is another, 

 sliced to show its internal chambers. At one side is a 

 magnified section of the common building stone of 

 Paris, the milioline limestone of the Eocene, so called 

 from its immense abundance of microscopic shells of 

 the genus Miliolina. At the other side is a magnified 

 section of one of the harder varieties of chalk, ground 

 so thin as to become transparent,* and mounted in 

 Canada balsam. It shows many microscopic cham- 

 * As for instance that of the Giant's Causeway, Antrim. 



