104 Ulrich en Correlation of the Lower Silurian. 
the Ohio river at Cincinnati. From Roger's Gap to Cincinnati 
the road bed gradually passes over all the strata exposed in the 
hills skirting the south bank of the Ohio river, the highest beds- 
exposed in the cuts being equivalent to those met with in the Cin- 
cinnati hills at a bight of about 375 feet above low water mark. 
As is well known, the lowest beds exposed in Ohio are seen 
in the bank of the Ohio river near Point Pleasant. These I 
regard as representing a horizon between fortv and fiftv feet 
lower than those seen at low water mark at Cincinnati. From 
the base of the Point Pleasant beds to the top of the Cincinnati 
series, there are nearly 800 feet of shales and thin la^^ers of 
argillaceous to crystalline limestone. To the southeast and 
northeast of Point Pleasant the beds dip more rapidly than to the 
westward, so that while the upper layei's pass under the river bed 
about eighty miles west of the Point, they already disappear at 
about forty-five miles eastward. To the north, northeast and 
northwest of Cincinnati they pass under the Upper Silurian de- 
posits, at distances varying from twenty-seven to seventy miles. 
In a general way the above briefly describes the distributioii 
of the members of the series as they are met with along a north 
and south line passing nearly through the center of the area of 
which they form the surface rocks. I now propose to take up 
successively each division, giving in moderate detail its litholog- 
ical characters, thickness, localities of outcrop, and other features, 
of interest, and, more particularly, the characteristic fossils. Of 
the latter the names of only such species as are known to occur 
in two or more of the four distinct areas will be mentioned. 
At the close of the paper some I'emarks relating to the distribu- 
tion and extent of the fauna will be in order. 
To prevent anticipation, I shall designate each bed that shows 
peculiarities of either a lithological or faunal character with its 
respective mmierals as it occurs in the section from below up- 
ward. This plan will be followed with all excepting the New 
York and Canadian sections. 
In the Kentucky section,' beds No. I, show a thickness of 
' The Lower Silurian rocks of central Kentucky have been ably re- 
ported upon by the lately deceased Mr. W. M. Linnej, assistant on the 
Kentucky geological survey. I bear willing testimony to his zeal and 
the unusual accuracy with which he has worked out the various beds. 
