366 STEVENSON 



" Coralline " forms from the lower layers of the Waterlime ; and 

 certainly some specimens in the New York University museum, 

 collected many years ago by John Gebhard, Jr., are in rock 

 showing the color and fracture not of Coralline but of Waterlime. 

 It is sufficiently evident that, while the great mass of Salina shale 

 was in process of deposit in central New York and in much of 

 the Appalachian region, the conditions within this portion of New 

 York changed so gradually as to bring about only a slow disap- 

 pearance of the fauna. There is a steady increase of calcareous 

 matter from the bottom to the top of the Waterlime. No fossils 

 were found in the, lower portions of No. i, but, above the middle, 

 Sphdfer vanuxei)ii and Lepcrditia alta were obtained from the 

 thicker layers, showing that the passage to Helderberg was quite 

 as gradual as that from Niagara. 



The Waterlime is the cave rock of this region. 



THE HELDERBERG 



The Helderberg (Lower Helderberg) was divided by the 

 older geologists into 



1. Tentaculite Limestone. 



2. Lower Pentamerus Limestone. 



3. Catskill or Delthyris Shaly Limestone. 



4. Scutella Limestone. 



5. Upper Pentamerus Limestone. 

 The succession being in ascending order. 



This succession is distinct in southern Pennsylvania and even 

 in southwest Virginia, though in the latter area the upper beds 

 are quite silicious. The formation is termed the Lewistown 

 limestone in the Pennsylvania reports. 



1. The Tentaculite Limestone 

 The passage from Waterlime to Tentaculite is marked in 

 the Schoharie region by an abrupt change in color, the latter 

 being the '' Blue limestone," with blue so deep in the lower lay- 

 ers as to appear almost black. The succession in descending 

 order is 



