Marcou.] 
76 
[Nov. 7, 
Rocky Mountains regions, we have another Olenellus horizon, with 
an immense development. In some places, as in Vermont and 
New York, Olenellus exists not only in the five or six hundred feet 
of the typical localities of Georgia and S wanton, but in a range 
of strata having a thickness of three or four thousand feet at least. 
And at the same time the Paradoxides so abundant at Braintree, 
St. John, Cape Breton and Eastern Newfoundland are entirely 
wanting, showing that a barrier of some sort existed between the 
Scandinavian, Eastern Newfoundland sea, and the Western New- 
foundland, St. Lawrence, Champlain, Hudson, etc., sea. 
The conclusion seems almost certain, that the Paradoxides hori- 
zon, with its Olenellus bed at the base of Scandinavia and Eastern 
Newfoundland, is contemporaneous with the Georgia, St. Albans 
and granular quartz strata of the St. Lawrence, Champlain and 
Hudson valleys, which are rich in Olenelli. By a difference in the 
geographical distribution, two great genera of Trilobites, the Olenel- 
lus and the Paradoxides, have developed parallel, mingling only in 
the eastern sea. And we may regard the Georgia formation of the 
Middle Taconic as the homotaxis of the St. John formation, in- 
stead of being younger and placed above it. The two formations 
being separated by dry land, which extended from Labrador to cen- 
tral Newfoundland, New York city and very likely farther south , 1 
we have on the two sides of that barrier, two primordial, contempo- 
raneous faunae, one containing very few Olenelli and a great devel- 
opment of Paradoxides ; while the other, on the contrary, shows an 
immense and remarkable development of Olenellus, without until 
now, a single example of Paradoxides. This is another case of 
what Mr. Barrande has called the great localization of the different 
primordial faunae, which se”em to be as numerous and as well marked, 
as the faunae actually existing in the different parts of our present 
oceans. 
POTSDAM NON-EXISTENCE. 
In that part of the province of Quebec under consideration, we 
have nowhere the Potsdam sandstone, except perhaps for one or 
1 During the Middle Taconic and Upper Taconic time, an arctic continent existed, 
from the Scandinavian primitive rocks to Scotland, Greenland, and Labrador (that 
continent may have extended farther east and west), and was united with an equatorial 
continent, by a narrow region, somewhat similar to the isthmus of Darien or Panama 
which connects the continent of North America with the continent of South America. 
That Taconic isthmus formed the barrier between the Atlantic and the Pacific ocean of 
that remote period of our globe. 
