152 



THE DAWN OP LIFE. 



inverted cone of carbonate of lime from an inch or 

 two to a foot in length, and with its point buried in 

 the mud at the bottom of the sea, while its open cup 



FIG; 38. Archaocyathus Minganensisa Primordial Protozoan. 



(After Billings.") 

 (a.) Pores of the inner wall. 



extends upward into the water. The lower part 

 buried in the soil is composed of an irregular acervu- 

 line network of thick calcareous plates, enclosing 



