10 THE AMERICAN MIDLAND NATURALIST 



dary. To the east they parallel the shore of Lake Erie, although here they 

 are very narrow. For the most part they are monotonously level and are 

 relieved only by the valleys of the streams which pass through them; drainage 

 is entirely to Lake Erie. 



They are intensely cultivated, particularly in the western portions, and to 

 the east, along the lake, they are utilized in addition for factory sites, summer 

 resorts and real estate developments. Except for the extensive lake marshes 



TILL 

 PLAINS 



BLUE gra: 

 REGION 



Map 1. The Physiographic Areas of Ohio (After Peattie). The Lake Plains 

 are characteristically level and are bounded by old beach lines marking the maximum 

 extent of Lake Maumee in postglacial times. Low rolling hills cover much of the Till 

 Plains area which is terminated on the east by the eastern limit of the Upper Devonian 

 shales. The Allegheny Plateau is more deeply dissected, especially in the unglaciated 

 portion, and the bed rock is chiefly sandstone, shale and conglomerate. The western 

 half of the state rests upon the limestone of the Cincinnati geanticline. The Blue Grass 

 Region is the only limestone country in the state which escaped glaciation. The glacial 

 boundary is indicated by the cross-hatched line. 



