i82 Ulrich on Correlation of the Lovcer Silurian. 
They have been hut Httle studied and so far as known, contain 
but few fossils, still, enongh has been learned to prove theai 
older than any exposed at Cincinnati. 
In central Kentucky the beds under consideration, (particu- 
larly the upper member) are known to contain deposits of bary- 
tes, lead, and zinc, while some of the layers arc occasionally 
porous, and hold small cavities filled with petroleum. A thin 
layer of sandstone is also present. Whether the recent flow of 
gas and oil in OhJb and Indiana is derived from them or from 
the equivalent of the "Blue Grass" beds immediately below 
them, is an interesting^ point that remains as yet undetermined. 
The ten beds or divisions so far treated, with the exception 
of VI and VII, consist mainly of more or le^s heavy bedded 
limestones. On the other hand, in the succeeding- beds of the 
Lower Silurian series of this area, soft, bluish shales or marls pre- 
dominate, and lavers of limestone over a foot in thickness are 
very rare. This lithological change is accompanied by an 
equally marked change in the fauna, since but a few species, 
comparatively, are common to beds X and succeeding deposits. 
The series intervening between beds X and the overlying 
Upper Silurian rocks have been the subject of much discussion. 
In the Ohio geological reports. Prof. Orton divides them into 
two sections, which he calls the Cincinnati and Lebanon beds. 
The first he again subdivides into three port'.ons named, in as- 
cending order, River Quarrv beds, Eden shales, and Hill Quarry 
beds. 
In the later Kentuckv reports Mr. Linney and others divide 
the series into three Actions which thev call the lower, middle 
and upper Hudson beds. 
Contrarv to the plan iisualU pur>ued, several reasons induced 
me to begin their discussion with a tabulated list of the fossils 
whose range in them has been approximately determined. The 
list embraces but a few more than half of the number of species 
known to me, but as the unnoticed forms are in most cases new, 
doubtful! V identified, or not fullv understood, they could not 
properly he included. Tvlanv of them, the undescribed forms 
especiallv, are characteristic of one or the other of the divisions, 
and thev doubtlesslv more than off-set the number which future 
