REVIEWS 



93 



tion. A great many of the sections and plates emphasize the importance 

 of the erosional surface on which the Berea sandstone often rests. 



The following classification of the rocks exposed in the region 

 under discussion gives the f ormational relationships as used : 



Pennsylvanian 



Sharon conglomerate 

 Royalton formation 

 Sharpsville sandstone 



Mississippian \ Orangeville formation 



Brecksville shale 

 Aurora sandstone 

 Sunbury shale 



Devonian 



Berea grit 

 Bedford formation 

 Cleveland shale 

 Chagrin formation 



On the evidence of its fossil content, the author has definitely corre- 

 lated the Chagrin formation with the Chemung of Western New York, 

 and the Huron shale in general is regarded as the western stratigraphic 

 equivalent of the Chagrin formation. The fact that the Cleveland shale 

 thickens to the south westward is observed to be due "largely to the 

 downward encroachment of the black deposits upon the Chagrin" and 

 to a similar "encroachment of the typical Cleveland black shales upon 

 the lower deposits of the Bedford formation." To the eastward, how- 

 ever, the Cleveland shale is found to decrease in thickness and to be 

 wanting in the sections near the Ohio-Pennsylvania line, possibly in all 

 those east of the Grand River valley. 



In the Bedford formation, the Euclid sandstone lentil near the base 

 and the Sagamore sandstone lentil at a somewhat higher horizon are 

 described. The disposition of the Bedford formation is not quite so 

 clearly made but it apparently either thins out entirely before the 

 Pennsylvania state line is reached or is represented by a part of the 

 Venango sandstones and shales, possibly including the Riceville shale, 

 of Pennsylvania. As evidence of its thinning out the finding of Chagrin 

 fossils in deposits below but very near the base of the Berea sandstone 

 is cited. "The results obtained in this bulletin seem to show con- 

 clusively that the Berea formation of Ohio is the western equivalent of 

 the sandstone of western Crawford County, Pennsylvania, identified 

 by Dr. White as the Corry sandstone and the subjacent Cussewago 

 shales and Cussewago sandstone." The sections given for this eastern 

 region show that the splitting up of the Berea sandstone begins at 

 least as far west of the Pennsylvania state line as Windsor Mills, near the 

 west line of Ashtabula County. 



