158 THE JOURNAL OF GEOLOGY. 



not alike for different sections which are geographically not 

 greatly separated from each other. 



The Catskill formation is primarily a local formation exhibited 

 in the Catskill mountain region of New York, distinguished phys- 

 ically as a series of sandstones and shales with greater or less 

 red-color, and by the absence of marine fossils, and the occasional 

 presence of shells and fish believed to have been of fresh or 

 brackish water habitats. It is the local expression of the broad- 

 ening shore condition of the continental elevation which brought 

 in the coal-making, or Carboniferous age of eastern North Amer- 

 ica. As 2l formation, it is separated from what went before by the 

 reddening, or graying of the sandstones and shales, their coarser, 

 more irregular structure, the departure of marine organisms, and 

 the occasional appearance of brackish water shells, fishes, and 

 some fossil drift-wood and plants. In relation to the time scale, 

 the period of beginning of this formation varies with the regions 

 in which it is exposed. At its extreme eastern extension, on the 

 peninsula of Gaspe, and in eastern New England, it began in the 

 Eodevonian Period. Along the Hudson River, it began at the 

 beginning of the Neodevonian, or perhaps before the termination 

 of the Mesodevonian. In the region of Oneonta and westward 

 it began soon after the beginning of the Neodevonian Period, and 

 then withdrew eastward, the marine conditions returning over the 

 region leaving the Oneonta formation as its record, and later in 

 the middle of the Neodevonian, it returned and continued on to 

 the close of the Devonian era. In the region of Bradford County, 

 Pennsylvania, it did not begin to be deposited till near the close 

 of the Neodevonian Period. Farther west the Clean Conglomer- 

 ate marks the final close of the Devonian Era, and the formation 

 in question did not begin till after the close of the Devonian. In 

 the eastern Pennsylvania and more southern sections, its age varies 

 with the locality. In general, it is terminated above by indica- 

 tions of the presence of permanent land conditions, either massive 

 beds of rounded pebbles or conglomerates, or thin beds of coal 

 or carbonaceous shales, or, in the absence of actual change in 

 formation, the line is arbitrarily set by the supposed tracing of 



