GEOLOGICAL SECTION OF NEW JERSEY 363 
ized by Dalmanites dentatus, the second by Orbiculoidea jervensis, 
and the third by the great abundance of Spirijer murchisoni. 
. In the Nearpass section the beds bearing the Dalmanites dentatus 
fauna are about 30 feet thick and form the crest of a high ridge which 
is the southern extension of the “trilobite ridge”? east of Tri-States. 
There is a mingling of Helderbergian and Oriskanian forms in this 
fauna, and there has been some difference of opinion as to whether 
these beds should be placed in the Port Ewen or Oriskany, but 
recent workers? unite in referring them to the Oriskany. 
Esopus grit—The Esopus grit which overlies the sandstones and 
siliceous limestones of the Oriskany forms the crest of Wallpack Ridge 
for the greater part of its extent in the state. It is a nearly black 
gritty rock with well-developed cleavage, which obscures the bedding 
planes. The fucoid “cauda galli” markings can frequently be recog- 
nized on the bedding planes when the latter can be distinguished. 
Apart from these markings fossils are very rare. The average 
thickness of the formation in New Jersey is estimated to be 375 
feet: 
Onondaga limestone—The Onondaga limestone overlies the 
Esopus grit along the northwestern slope of Wallpack Ridge. 
Toward its base the formation is somewhat shaly and there ‘is 
apparently a rather gradual transition from the grit to the limestone. 
The latter is hard, cherty, and regularly bedded in layers ranging 
from three inches to one foot in thickness. ‘The beds are assigned 
to the Onondaga on the basis of their position and lithology rather 
than faunal evidence, since the recognizable forms are not sufficiently 
characteristic for close correlation. 
Marcellus shale-—Fissile black shale, referable to the Marcellus, 
has been reported to occur in New Jersey along the bed of the Dela- 
ware River a few miles below Port Jervis, but in recent years the 
exposures have apparently been buried by silting-up of the channel. 
This is the highest of the Devonian beds exposed in the state along 
the Delaware River, but in the Green Pond Mountain area still 
younger beds occur. 
t Shimer, New York State Museum Bulletin 80, pp. 175 f. 
2 Weller, Geol. Surv. of N. J., Paleontology, Vol. III, p. 96. Shimer, of. cit., 
p. 184. 
