290 PRIMORDIAL FAUNA AND POINT LEVI FOSSILS. 
only ; while the typical form of Dendrograptus occurs in the Potsdam 
sandstone, and, likewise, in three other species, in the Quebec rocks. 
We find, therefore, in the other genera except trilobites, very little 
satisfactory evidence on which to rely in the present state of our 
knowledge, for determining the position of these strata. 
In the present discussion, it appears to me necessary to go further, 
and to inquire in what manner we have obtained our present ideas of 
a primordial, or of any successive faunze. I hold that in the study of 
the fossils themselves there were no means of such determination 
prior to the knowledge of the stratigraphical relations of the rocks in 
which the remains are inclosed. There can be no scientific or syste- 
matic paleontology without a stratigraphical basis. Wisely then, and 
independently of theories, or of observations and conclusions else- 
where, geologists in this country had gone on with their investigations 
of structural geology. The grand system of the Professors W. B. 
and H. D. Rogers has been wrought out not only for Pennsylvania 
and Virginia, but for the whole Appalachian chain; and the results 
were shown in numerous carefully worked sections. In 1848, ’44 and 
?45, I had myself several times crossed from the Hudson River to the 
Green Mountains, and I found little of importance to conflict with 
the views expressed by the Professors Rogers in regard to the chain 
farther south, except in reference to the sandstone of Burlington, and 
one or two other points, which I then regarded as of mmor importance. 
Sir William Logan had been working in the investigations of the 
geology of Canada; and better work in physical geology has never 
been done in any country. ne 
This then was the condition of American geology, and investigators 
concurred, with little exception, in the sequence based on physical 
investigations. As I have before said, our earliest determinations of 
the successive faunze depend upon the previous stratigraphical deter- 
minations. This, I think, is acknowledged by Mr. Barrande himself, 
when he presents to us, as a preliminary work, a section across the 
centre of Bohemia. With ali willingness to accept Mr Barrande’s 
determination, fortified and sustained as it is by the exhibition of his 
magnificent work upon the trilobites of these strata, we had not yet 
the means of parallelizing our own formations with those of Bohemia 
by the fauna there known. The nearest approach to the type of 
primordial trilobites was found in those of the Potsdam sandstone of 
the north-west, described by D. D. Owen; but none of these had 
