10(> The American Geologist. Feb. 1891 
water conditions. in the presenl instance there is a probability 
that shallow water conditions were prevalent: the evidence for this, 
however, is not given by the bryozoan fragments, but by the peb- 
bles in tin Belfast conglomerate^ only thirty-two miles southeast of 
tiie Todd Fork locality. 
Do these tacts prove the existence of the Cincinnati anticlinal 
in Clinton times 7 Certainly not; they merely suggest the exist- 
ence of shallow water conditions over certain areas in Ohio, on 
the eastern side of the anticlinal crest. They do not exclude 
similar conditions over Clinton areas now low down on the flunks 
of the anticlinal. The probability is that shallow water condi- 
tions prevailed from Cincinnati group to Clinton times, in south- 
western Ohio. To what extent these conditions were general in 
neighboring areas is not shown by the facts cited. 
In the Niagara and Lower Helderberg groups succeeding the 
strata just discussed, the general supply of calcium carbonate de- 
creases and that of magnesium carbonate increases. The result 
finds its expression in the few layers of true limestones, and in 
the general prevalence of dolomitic rocks. In the earlier strata 
of Devonian age the decrease of calcium carbonate becomes still 
more general, silica and clay ingredients appear abundantly and 
at less fitful intervals. The result is the continued appearance of 
dolomitic rocks, and the increase of shales as characteristic and 
important parts of the geologic series. In later Devonian strata 
the calcium carbonate plays an inconspicuous part: silica and clay 
ingredients form prominent constituents of the rocks. Kven 
dolomitic rocks are scarce or altogether absent, and shales form 
the great mass of later Devonian strata. In Waverly strata east 
of the anticlinal, actual sandstones in which quartz is the promi- 
nent constituent begin to be prevalent, and in some parts of this 
formation the quartz grains are of sufficient size to be called pel) 
I ilcs. The quartz pebbles increase in size in later formations, and 
at the opening of the Carboniferous age, strata are found which 
fully merit the title — quartz conglomerates. 
Now it is evident that the pebbles <>f these quartz conglomer- 
ates were not derived from the limestone areas of the Cincinnati 
anticlinal axis. Prof. Claypole has shown a general increase in 
the size of these quartz pebbles towards the east and has inferred 
a source from that direction. It is evident however that none of 
