208 REPORT OF THE AMERICAN COMMITTEE. 
faunas, the greatest physical break in the series of the Lower 
Paleozoic being at the top of the second fauna rocks. All others 
would divide the rocks of the first fauna locally, or would follow 
the classification proposed by Mr. Walcott, viz. : Upper, or Pots- 
dam ; Middle, or Taconic ; and Lower, or Acadian ; the Upper 
including the Potsdam and Lower Calcifcrous and the Knox and 
Tonto groups; the Middle including the Taconic, Georgia, 
L'Anse an Loup, and Prospect groups; and the Lower including 
the St. John's, Braintree, New Foundland, Wasatsch, and Ten- 
nessee groups. 
Respecting the use of the terms Menevian and Ordovician, 
there is a pretty general concord of opinion, when any is ex- 
pressed, in the negative; although Messrs. Hunt and Walcott 
are disposed to regard the term Ordovician as useful and ap- 
plicable to the second fauna rocks in America, in discussing the 
relations of the faunas. 
Your reporter, therefore, feels bound, regardless of his own 
convictions, but urged by the opinions of a large majority of all 
American geologists who have communicated their views to him, 
and by the known opinion of others, to consider the introduction of 
the term Taconic in some manner into the nomenclature of the 
Lower Paleozoic as imperatively demanded in deference to those 
geologists who have given long study and hard labor to the sub- 
ject, and who alone should be considered competent to advise. 
This step being determined upon, it becomes necessary to decide 
how and where this term shall be inserted in the stratigraphic 
column. 
It became evident at once that the place for the term Taconic 
is in connection with the first fauna, and not the second. It 
would be in violation of a simple and well-known canon of no- 
menclature to so divorce a term from its original use and defini- 
tion by its author, that it should have no application to the object 
described by the author. 
It also became evident, on short reflection, that the recom- 
mendation of Mr. Walcott, while giving exact justice to Mr. 
Emmons, in using the term for that part of the Taconic which 
under his searching scrutiny has yielded an abundant primordial 
fauna, may be extended as a faunal designation, without injustice 
to any other claimant, so as to cover the whole primordial zone. 
For reasons which were given in a paper which I had the 
