THE PEXXSYLYAXIAX PERIOD. 



545 



Fig. 240. — Map showing the areas where the Pennsylvanian system appears at the 

 surface in North America. The map also shows, as in preceding similar cases, 

 the areas where the Pennsylvanian system is thought to exist though buried 

 (lined areas>; the areas where it is thought once to have existed, but to have been 

 removed by areas (dotted); and by inference the relations of land and sea during 

 the Pennsylvanian period. 



