382 



HISTORICAL GEOLOGY 



sometimes below. During the Pennsylvanian period many 

 hundreds of feet of strata with many distinct coal beds accu- 

 mulated. 



Coal Measures in Europe. The marshy plains were 

 duplicated on a smaller scale in western Europe ; and, from 

 the coal seams there formed, England, Germany, and adjacent 



FIG. 402. 



Little wheatlike shells of protozoans (Fusulina) in a Pennsyl- 

 vanian limestone. 



countries now derive most of their supply of coal. Russia, 

 the Mediterranean region, and southern Asia, however, were 

 occupied by clear, open seas in which thick beds of limestone 

 were deposited. In some places these strata are so full of 

 the little wheatlike shells of the protozoan Fusulina (Fig. 402) 

 that they are generally known to geologists as the " Fusulina 

 limestone." 



LIFE OF THE COAL SWAMPS 



Plants well recorded. Plants are known to have been 

 plentiful in the Devonian, and there is reason to believe that 

 they clothed the land surfaces even in much earlier periods; 

 but by the accident of having large coal beds preserved, we 

 have in the Pennsylvanian rocks for the first time a satisfac- 

 tory record of the plants of the land. 



Dominance of the fernlike forms. As in our modern 

 swamps, so in those of the Pennsylvanian period, plants of all 

 sizes lived together in the wet places. Little floating algae, 

 hardly visible to the eye, low sedgelike forms, and even large 

 trees were present. But there was this difference : the plants 

 belonged more largely to the lower branches of the vegetable 

 kingdom. Neither the cypress nor the mangrove, nor even the 



