UPPER PALEOZOI3 (dEVONIC). 247 
grits, or we may settle the question, which at present is variously- 
interpreted by American geologists. The use of such combina- 
tions helps little ; it is merely an expression of ignorance or of 
imperfection of the classification. The real question is, Shall we 
draw arbitrary lines, and if so, where in a given standard section 
shall the line be drawn ? It matters little on which side of the 
Oriskany the line be drawn, but wherever it is put it is better for 
American geologists to have a uniform usage than to attempt to 
mediate by saying passage beds, for the same difficulty will be 
found everywhere in the series, unless there be a gap, or uncon- 
formity, and any particular formation may be regarded as a passage 
bed from the one below to the one above. The New York Sur- 
vey has set the precedent of placing the Oriskany at the top of 
the Silurian, from which precedent I have already given reasons 
for dissenting. 
(3) The third problem demanding settlement is as to the divi- 
sion of the Devonian. Do we wish to have a uniform system of 
subdivision for the Devonian system ? This is partly answered 
by the facts already presented. No stratigraphical or lithological 
subdivision of the Devonian is possible which shall be applicable 
to all of the several types of that system in America. Almost 
the same may be said of faunas, but it is discovered by comparison 
of sections that the eastern Appalachian sections present the same 
genera] succession of faunas as is seen in the English and Euro- 
pean sections. Shall we then adopt a trifold subdivision of the 
Devonian, giving names if necessary, or using merely the general 
terms lower, middle, and upper, which, as they are arbitrary 
divisions of the Devonian system, are to be preferred. In the 
latter case, the top of the Corniferous limestone is the best point 
of division between lower and middle, and fairly corresponds 
faunally with European usage. The division between middle 
and upper, if we seek uniformity with European usage, should 
be placed below the black shales, the Genesee shale of New York ; 
and where theTully limestone is present its special fauna should 
be included in the upper Devonian, as it undoubtedly corresponds 
with the Cuboldes fauna of the Frasnien of Belgium and of the 
base of the upper Devonian of England and equivalent beds, the 
RhynchoneUa cuhoides being there associated with the Spirifcra 
( Verneulli) dlsjuncta, which with us, however, does not appear 
till still higher in the typical Chemung fauna. 
