UPPER PALEOZOIC (dEVONIC). 237 
lithologlcal composition or sequence which is uniform for the 
several areas. 
In seeking uniformity of nomenclature the study of the Amer- 
ican Devonian leads to the following conclusions : 
(1) That uniformity is desirable in the names and prominent 
distinctive biological characters of the so-called systems. 
(2) That valuable results may be reached by a discussion, on 
the part of those acquainted with the same system in the differ- 
ent parts of the world, as to the best biological criteria for mark- 
ing the boundaries of the systems. 
(3) That while uniformity is possible in subdividing a system 
into parts, the number of such parts, and the characters distin- 
guishing them, must be determined after a wide, comprehensive 
and minute study of their biological characters. 
(4) That preliminary work in classifying rocks should not 
seek uniformity, but should adopt local nomenclature, and that 
nomenclature based upon an exhaustive comparison of represen- 
tative sections can alone reach a uniformity that will be of per- 
manent value. 
§ 3. The Base of the Devonian. 
The precise point of division between the Silurian and the De- 
vonian has not been uniformly determined. After finally adopting 
the equivalency of the New York Corniferous rocks with the Devo- 
.nian of English authors — not the Silurian, as was at first thought 
correct,--the New York geologists placed the base of the De- 
vonian at the top of the Oriskany sandstone. In 1847, De Ver- 
neuil, making a comparison of the American geological series with 
the European, in the Bulletin of the Geological Society of France, 
urged the propriety of regarding the Oriskany as the base of the 
Devonian, the chief reason being the appearance in the Oriskany 
of the first Spirifers with bifurcating plications, a common char- 
acter in the Devonian and particularly in the Carboniferous. In 
1859, 3d vol. of Paleontology of New York, Professor Hall 
objected, and proposed that the Oriskany should be regarded as 
the top of the Silurian, because the first vertebrates then known 
in our series were found above in the Schoharie grit. 
Neither of these arguments are of any value now, as verte- 
brates have been found below the Oriskany, and as the type of 
Spirifer referred to by De Yerneuil begins in the Niagara (Dana). 
