UPPER PALEOZOIC (dEVONIC). 235 
Conclusions. 
There are thus, 1st, a northeastern border area, mainly com- 
posed of coarse, arenaceous deposits, thick, and with little to 
distinguish it into subordinate zones. 
2d. An eastern continental area, with sandstones, limestones, 
shales and conglomerates alternating with each other, and pre- 
senting a rich and varied series of faunas, marking a considerable 
number of distinct zones which follow in a constant order. 
3d. A central continental area, mainly limestone and soft 
argillo-calcareous shales, and, compared with the more eastern 
sections, very thin ; presenting a fauna which represents the 
whole eastern Devonian and is plainly a sequent to an under- 
lying upper Silurian fauna. It is followed by a Carboniferous 
fauna to which it is generically closely related, and about its 
border is terminated by a black shale. 
4th. A western area represented by a thick massive series of 
limestones followed by black shales, not separated into distinct 
faunas, but carrying a common fauna showing but slight change 
from bottom to top. 
With all these great contrasts in lithological, stratigraphical 
and paleontological characters, the evidence is satisfactory that the 
several sections are representatives of the same geological age ; 
that, taken as wholes, they do not represent parts, the one taking 
the place of an interval in the other, but they cover approximately 
the same interval, and probably represent approximately the 
depositions of the same length of geological time. 
They are bound together, and their relationship certified to 
by the fossils they contain. The relationship is recognized in 
the combination of species to form faunas and in the varietal 
modification of species, as well as in the identity of the species 
themselves. AVe cannot find stronger contrasts across the Atlan- 
tic eastward than are found across the continent westward. The 
principles which the American geologist is required to aj)ply in 
discussing the geology of his own domain are no less broad tlian 
those which the International Congress meets with when it 
attempts to unify nomenclature for all the world. Wherever 
unification is practicable in America it is practicable for all the 
world, and where America fmds unification a cumbrance it is use- 
less for an International Congress to attempt it. 
