THE M1SSISSIPPIAN PERIOD. 



497 



^S 



Fig. 228. — Map showing the areas, in black, where the Mississippian system appears 

 at surface. The map also shows where the Mississippian system is thought to 

 exist, though buried (the lined areas), and the areas from which it is thought to 

 have been removed by erosion (the dotted areas). By inference, also, the map 

 shows the relations of land and water during the Mississippian period. 



