REPORT OF THE STATE PALEONTOLOGIST 1902 1149 



Let us now inquire if 1hese are the only rocks at this place 

 which belong to this epoch. 



We find lying between this coralline limestone and the tentacu- 

 lite limestone of the Lower Helderberg some 40 feet of rock, of 

 which most of the layers are used in the manufacture of cement, 

 and this feature holds good for some distance to the north and 

 south of this point, but under quite different circumstances. At 

 the Vlight Berg we have several courses or layers lying together, 

 to the thickness of about 22 feet, all of which is used in the 

 manufacture of cement, hitherto known as waterlime, and quite 

 generally regarded as wholly belonging to the Waterlime group. 

 The upper layers of this waterlime are of a light grayish drab in 

 color, but those that lie directly upon the coralline limestone are 

 nearly black. There is about the same thickness of each, and 

 they are known by the quarrymen respectively as the light and 

 dark cement. Now as we go either north or south, even no 

 further than the Steep Rocks on the one hand, or Wilbur on the 

 other, we find these light and dark cements separated; and 

 between them is found another layer of limestone [= Cobleskill], 

 so that instead of one thickness of cement rock of 22 feet, we 

 have two of 12 or 15 feet each, the light colored lying above, and 

 the dark below this intermediate layer. This last represents the 

 general features and disposition of the rocks in nearly, if not 

 quite all of the cement quarries in Ulster county, except those 

 of the Vlight Berg. Dr S. T. Barrett, of Port Jervis, has made 

 the rocks of the lower Helderberg and those immediately below 

 thein, in his vicinity, a special study for some time, and he is 

 inclined to the opinion that our black cement rock and the over- 

 lying coralline limestone, where that occurs, belong to the Niagara 

 epoch, and I am led to the same view for the following reasons. 

 The dark cement rock quite often presents a coralline structure, 

 and the fossil molluscae and trilobites found embedded are such 

 as seem to belong to the Niagara epoch. I have one of the 

 latter which is nearly perfect, although it has been subjected to 

 the burning process of the kilns. It answers every requisite of 

 the Calymmene niagarensis, except as to size, it being 

 somewhat larger than other specimens I have seen. The coral- 

 line layers above the dark cement, where they prevail, have many 

 specimens of Halysites, or chain coral, embedded in them, which 

 Dr Hall says are not found above the Niagara. If this conclusion 

 is correct regarding the proper classification of these rocks, we 

 have existing at the Vlight Berg a state of stratification quite 

 peculiar, in that the layers belonging to the Niagara epoch that 

 are suitable for the manufacture of cement directly underlie the 

 layers of the waterlime, so extensively used for the same purpose, 

 and which so generally form the base of the Helderberg group. 



