CHAPTER V. 
FORMATIONS OF DEVONIAN AGE. 
COEYMANS LIMESTONE. 
The Helderbergian faunas in New Jersey do not differ essentially 
from those in New York. The same faunal zones are recognized, and 
nearly all of the species identified are New York forms, which are 
in no way different from specimens occurring in the typical Helder- 
bergian localities. 
The Coeymans limestone is the first of the Helderbergian forma- 
tions, and in the Nearpass section it has an estimated thickness of 
- forty feet, though only the lowermost beds are actually exposed. It 
lies upon the Manlius limestone, in the top of the Nearpass bluff, 
differing from the subjacent formation in its coarser and more crystal- 
line texture and in its lighter color. Frequently more or less chert 
is mingled with the limestone. The lithologic transition from the 
Manlius to the Coeymans limestone is not abrupt, but is accomplished 
within a thickness of a few feet. 
The Coeymans fauna is far more prolific than that of the Manhus 
limestone, and has an altogether different composition. The most 
characteristic species of the fauna, wherever it occurs, is Gypidula 
galeata, and the faunal zone included in the Coeymans limestone may 
be spoken of as the Gypidula galeata zone. In the basal portion of 
the formation there are frequently numerous masses of the coral, 
Favosites helderbergiv, usually more or less completely silicified, as- 
sociated with masses of a concentrically laminated stromatoporoid. 
This coral bed in the Coeymans limestone of New Jersey is doubtless 
the southern extension of the coralline bed at the base of the same 
formation in New York. 
No complete section of the Coeymans limestone has been exposed 
in New Jersey, and usually it is the lower portion of the formation 
which is exposed in the outcrops. If the beds could be studied in 
detail throughout the entire thickness of the formation several sub- 
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