8 
PALAEONTOLOGY OF NEW-YORK. 
differing little in its general characters from the Potsdam sandstone which 
lies below, except perhaps in a lighter color and more friable and in¬ 
coherent texture. 
So far as observed, there are no alternations of the Calciferous with the 
sandstone which succeeds it; though where the former is broken up, and 
presents the brecciated character before described, fragments of the higher 
sandstone are mingled in the interstices throughout the rock below. There 
are, moreover, sometimes evidences of faults or down-throws of the lower 
rock, by which the higher sandstone is brought into a lower position. 
In its eastern extension, this upper sandstone thins out somewhere in 
the northern part of Wisconsin, or the adjoining State of Michigan, since 
it has no existence in a section along the Escanaba river, on the north of 
Lake Michigan. It may also be stated, that in the general thinning out of 
all the lower limestones, the Chazy limestone is scarcely recognized west 
beyond the great northern curve of these rocks about the head of Lake 
Michigan. 
It will be observed, therefore, that this upper sandstone of the west 
holds in the series precisely the place of the Chazy limestone, as will 
appear on comparing the column of strata in New-York with that in the 
west : 
New-York. 
Trenton limestone. 
Black-river limestone. 
Birdseye limestone. 
Chazy limestone. 
Calciferous sandstone. 
Potsdam sandstone. 
Iowa, Wisconsin and Minnesota. 
Trenton limestone. 
Galena limestone. 
Black-river limestone. 
Birdseye limestone. 
Sandstone of the Chazy period. 
Calciferous sandstone. 
Potsdam sandstone. 
While in New-York and Eastern Canada the conditions giving origin 
to the Calciferous sandstone were succeeded by seas capable of sustaining 
a numerous fauna, with coral reefs and all the phenomena attendant upon 
the great limestone formations, this period at the west was followed by 
precisely a repetition of the conditions which preceded the deposition of 
