of the Older Formations of the United States. 15 
. maybe so extremely rare, that they cannot be relied upon. 
We can thus easily perceive how these strata, when in prox- 
imity to hypogene or metamorphic rocks, and where the supe- 
rior connexion is obscure, may be mistaken for the older slates, 
reliance being placed upon the presence or absence of organic 
remains. 
‘Such were the different conditions of this wide expanse of 
ocean during the period which elapsed from the commencement 
of organization to the period when this system of rocks termi- 
. mated. We must now be prepared for even greater changes 
. in this ocean, both in its organic contents and in the compara- 
tive conditions between its eastern and western extremes. 
. Succeeding what we have denominated the Chemung 
_ Group, we find in New York a considerable deyelopment of 
: red sandstones, greenish and red shales and gray sandstones 
with conglomerates. The whole series constitutes the equiv- 
. alent of the Old Red Sandstone of Europe. This series is 
| distinguished from the rocks below, not only by its different 
» lithological character, but by its organic remains, which clearly 
. Mentify it with the formation just named. 
— . Its greatest thickness may be about two thousand feet in the 
5 eastern part of New York and in Pennsylvania, but it thins rap- 
idly westward, and in New York, can scarcely be identified be- 
Yond the Genesee River. Here is the most rapid thinning out of 
‘Vast thickness of strata which, so far as we know, do not réap- 
pear ina westerly direction. The organic remains consist of 
few shells, unlike those below, with an immense number of. s 
ates and fragments of the bones of fishes. In this rock within 
le State of New York, no species of the Brachiopoda have | 
been found ; the only fossils, besides the scales and bones of 
_ ‘shes, being a shell allied to Cypricardia and great nambers of 
. Vegetable remains, a ea 
___ Succeeding the Old Red Sandstone is a coarse conglomer- 
5 made up of white quartz, pebbles and coarse sand. 
Now after the thinning out of the former rock, this conglom- 
Tests upon the rocks of the Chemung Group. This is- 
^c 
