UPPER PALEOZOIC (dEVONIc). 243 
nomenclature, are met with in the Devonian of North America. 
On the other hand, if uniformity of nomenclature is desiraljle 
anywhere, certainly it should be applied here. But, as we have 
seen, the physical characters of the stratigraphy, or the litho- 
logical constitution of the rocks, are of little or no value in de- 
termining the true equivalency of stratified deposits found in 
distinct geographical areas. 
In seeking to determine the place in the column of any newly 
examined set of rocks, there can be no question that, if they are 
fossil-bearing, the fossils are the critical tests. Thus we deter- 
mine that the Iowa Devonian is a representative of middle and 
upper Devonian of New York, and in the Gaspe series the dis- 
covery of Rensselaeria in the sandstone 1000 feet above the lime- 
stone, leads us to synchronize that horizon with the New York 
Oriskany. In this way, also, the limits of the Devonian strata 
in New York were found by a comparison of their fossils with 
the Devonian fossils of Philli)is, or with the Rhenish or Belgian 
fossils, as was done by De Verneuil. This reveals one usage 
that is common to us all ; in determining equivalency of geo- 
logical horizon for areas between which there is no known con- 
tinuity of strata, the fossil contents are the determining criteria. 
And there is a second rule involved in this operation ; in attempt- 
ing to compare and thus unify nomenclature in the classification 
of geological deposits, there is a typical section which is taken as 
the standard, and with it the new sections are compared. 
This leads to the consideration that in order to reach uni- 
formity in usage of nomenclature we must first adopt uniform 
standards. For the Paleozoic, as high as to the top of the Devo- 
nian, the New York section is practically the adopted standard 
for North America. But in the grand divisions, as is evident 
from the terras Devonian, Silurian, Cambrian, and in the minor 
subdivisions if we closely study them, there is found a prior 
standard which has been the basis for classification, if not of 
nomenclature, in this "New York system." 
Taking our example, the Devonian, the influence of a lower, 
middle and upper Devonian is felt in the classifications of all 
the Devonian areas in the world. While we are accustomed to 
take the standard of New York, and to place the termination of 
the lower Devonian at the top of the Corniferous limestone, and 
of the middle Devonian at the top of the Genesee shale, this sub- 
