LOWER PALEOZOIC. 199 
covering the periods, (3) Trenton ; (2) Chazy (embracing Chazy 
and Calciferous) and (1) the Cambrian. 
To this use of the term, or the preceding, I would give my 
assent. 
V^ery truly yours, 
James D. Dana. 
Recommendation of Mr. S. W. Ford. 
The opinion of Mr. S. AV. Ford is expressed in the following 
brief communication : 
ScHODACK Landing, N. Y., August 2d, 1887. 
Prof. IST. H. Winchell : 
My Dear Sir : Your favor of June 26th, requesting an ex- 
pressi(m of ray views concerning the nomenclature of the Ameri- 
can Lower Paleozoic, is at hand. 
I fear that I have given less attention to this subject of late 
years than its importance has deserved ; but my classification 
and chronological arrangement of the American formations, from 
the Acadian or Paradoxides beds to the top of the Lorraine or 
Hudson River group, would at present be as follows: 
1 . The rocks, from the base of the Calciferous sand rock to the 
top of the Lorraine, I should call " Lower Silurian," retaining 
the names by which they are at present known for the several 
subdivisions thereof. The " Quebec Group" of the Canadian 
geologists appears to me to be about the equivalent of the Cal- 
ciferous and Chazy of the New York geologists. 
2. The three great fossiliferous formations below the Calcifer- 
ous, viz., the Potsdam, Lower Potsdam (or Georgian), and Aca- 
dian, I should call collectively Cambrian, and regard them as 
constituting a system as distinct from the Silurian as is the latter 
from the Devonian. For its middle portion, or that marked by 
the genus OleneUus, I would advocate the adoption of the term 
"Taconic," as a deserved tribute to the labors of Dr. Ebenezer 
Emmons. 
Geologists may differ as to the propriety of drawing the line 
between the American Silurian and Cambrian at the base of the 
Calciferous, but I am convinced that there is a faunal change at 
that horizon of sufficient importance to demand it. 
