HELDERBERG DIVISION. 
343 
brown, red and black; and it is sometimes slightly calcareous. The fossils are crystalline 
carbonate of lime ; but on the surface of the earth, the moulds of the fossils only remain. In 
the First district, it rarely exceeds two feet in thickness, and in many places is not more than 
eight inches, and in some places is absent; but it is extensive, strongly marked in its fossil 
contents, which are of a large size, and generally attracts the attention of persons travelling 
along the roads. In Pennsylvania, Maryland and Virginia, this rock attains a great thickness 
and development (several hundred feet). 
The rock is well exposed in the hills east and west of Schoharie, various places on the 
Helderberg in Bern, Knox and Bethlehem, and occasionally as it ranges southward to Eso- 
pus falls, beyond which it was not recognized. 
^ 6. Delthyris Shaly Limestone, or Catskill Shaly Limestone. 
Fig. <20. 
The Delthyris shaly limestone, a name perhaps scarcely appropriate to the whole mass of 
strata included in it, is one of the thickest and most extensive members of the Helderberg 
division. It is properly composed of three distinct masses, viz. upper, middle and lower, 
which are as dissimilar in lithological and zoological characters as any of the other members 
of the Helderberg division. 
