24 PROTOZOA. FORAMINIFERA. 



of a supplemental skeleton, and they are regarded merely 

 as crystals of metaxite. Similarly the stolon passages are 

 found to be simply crystals of pyrosclerite. The mode of 

 occurrence of Eozoon also furnishes corroborative evidence. 

 It has never been found in any unaltered rock, and no other 

 fossils have been discovered in association with it. In the 

 case of the specimens found at Chelmsford and Bolton, 

 U.S.A., it has been shown that the limestone in which the 

 Eozoon occurs was not formed at the same time as the 

 gneiss with which it is associated, but that it has been 

 introduced subsequently in the manner of a vein, so that 

 here at any rate Eozoon cannot possibly be organic. 



Distribution of the Foraminifera. 



The majority of the Foraminifera are marine, most of 

 them living on the sea-bottom. A few however, as for 

 instance Globigerina, exist at or near the surface in the 

 open ocean, and these few forms are very important on 

 account of their great abundance. The earliest examples 

 of the Foraminifera are found in the Ordovician rocks, 

 but they are rare until we reach the Carboniferous, some 

 of the limestones of which are formed largely of them, as 

 for instance, the $accamma-limestone of the North of 

 England and Scotland, and the Fusulina-Umestoue of 

 Russia, America etc. The order continues to be well 

 represented throughout the Mesozoic formations, particu- 

 larly in the Chalk, and it attains its greatest development 

 in Tertiary and recent times. In the Eocene the genus 

 Nummulites is extremely abundant, forming the massive 

 Nummulitic Limestone of Southern Europe, Egypt, Asia 

 Minor, and the Himalayas. 



