176 The American Geologist. ^^''^^h. isos. 
tion the Rondout is reduced to four and one-half feet, but 
which at Schoharie has a thickness of thirty-nine feet. 
To the west of Schoharie, about Litchfield, Herkimer coun- 
ty, the Manlius including the Rondout and Cobleskill mem- 
bers, hais a thickness of no feet, beneath which is a covered 
slope of about sixty feet to the true Waterlime or Bertie form- 
ation with the Eurypterus fauna. In other words, the over- 
lapping of the successive younger formations is from the west 
and south to the east and north. In Herkimer county the Clin- 
ton is not followed by the Niagaran, but at once by the Salina. 
Farther east the Clinton also fails, and at Schoharie, after 
nineteen feet of the pyritiferous shales, there follow at once 
the Cobleskill, the Rondout, with the Coralline fauna, the Up- 
per Manlius, and then the Helderbergian. Here the united 
thickness of the Cobleskill, Rondout and Upper Manlius is 
ninety-one feet, while about Litchfield the same zones are no 
feet thick. Therefore, the pyritiferous shale of Schoharie can- 
not be the Clinton, but probably is the thinned eastern edge 
of the lower part of the Cobleskill of the Litchfield section 
and not of the true Waterlime or Bertie formation. 
From a faunal standpoint the Cobleskill shows clearly that 
it cannot be the eastern representative of the western Niagara. 
There is not a species common to the two' formations. This 
fact was noticed by Hall in 1852 — though less emphatic — when 
he described the fauna, since he distinctly queried all the sup- 
posed specific identities. The presence of Halysites had some 
influence in this correlation, but certainly this genus alone can- 
not make this fauna Niagaran, since it is known to range from 
the Black River upward into the Manlius. 
An analvsis of the Cobleskill fauna also shows it to be 
younger and more advanced than that of the Niagara and al- 
so that it is not a direct development out of the latter. The 
diagnostic Niagaran types are not present in the Cobleskill 
fauna, while the latter is clearly the precursor of that of the 
Tentaculite limestone. This view is further sustained by the 
species in common (four out of thirty-one) to both horizons. 
Tracing the Cobleskill and Manlius faunas southward, the 
writer has noticed that both are very persistent throughout 
New Jersey, Pennsylvania, into Maryland and West Virginia. 
In the same direction it has also been seen that the Ontaric 
