FORAMINIFERA 133 



partly thin particles of sand. There are also those 

 whose shells are entirely made up of sand-grains 

 cemented together. 



Notwithstanding their minuteness, with few excep- 

 tions, the shells are partitioned into many chambers. 



Fig. 39. A Encrinite Limestone. B Niunmulitic Limestone. 

 C Coralline Limestone. 



Picture such a complex structure in a shell sufficiently 

 small to drop through the eye of a needle ! Many of 

 the forms of shells are spiral, and are like those of 

 the nautilus and ammonite. Some Foraminifera 



