216 REPORT OP THE AMERICAN COMMITTEE. 
contain a fossil of the first fauna or a formation that contains 
one elsewhere. The "Upper Taconic" slates lie west of the 
range, and the " Granular Quartz" series east of it; and the 
range is formed of strata of the Trenton-Hudson Terrane. 
2d. — The " Taconic System " was considered pre-Potsdam on 
two suppositions : («) that the Calciferous sand rock of the Lower 
Silurian is unconforraably superjacent to the Taconic slates on 
the west; (b) that the variation of the lithologic characters of the 
Lower Taconic rocks, from the New York Lower Silurian, in- 
dicates a distinct system of rocks. We find that the uncon- 
formity (a) was based on errors of field observation, and (6), that 
the " Lower Taconic" rocks are of Lower Silurian age, with the 
exception of the lower quartzite, which is Cambrian and conform- 
ably subjacent to the Lower Silurian. 
3d. — The claim of priority of discovery of the Primordial 
fauna is invalidated by the fact that the fossils found in the 
Taconic slate were referred to a pre-Potsdara horizon on an 
erroneous interpretation of the stratigraphy and not from com- 
parison with a known fauna that had been stratigraphically lo- 
cated in any clearly defined geologic section. 
4th. — It is only a fortunate happening, and not a scientific in- 
duction based on accurate stratigraphic or paleontologic work, 
that any portion of the " Taconic System " is found to be where 
Dr. Emmons placed it. 
5th. — The application of the principles stated at the beginning 
of this paper rules out the name Taconic from geologic nomen- 
clature. 
6th. — The term Cambrian antedates Taconic for a strati- 
graphic system, and, also, as a correctly-defined faunal defini- 
tion. 
It was stated under " Discussion " that Professor Dana held 
the opinion that the "Lower Taconic" was the typical "Taconic 
System" as first defined in 1842, but as that was proven to be 
Lower Silurian in age, the " Taconic System " could not longer 
be recognized.* For a time I was inclined to disagree with this 
view, but as I approach the end of this investigation I am 
convinced, after a full consideration of all the circumstances, 
that the position taken by Professor Dana is the correct one. 
The first published section of the " Taconic System " gives all 
* American Journal of Science, III. vol. xxxi., pp. 241-244, 1886. 
