GEOLOGIC FORMATIONS OF NEW YOKE 



165 



Catskill group 



The Chemung passes or changes eastward into the Catskill, an 

 enormous series of shaly and sandy strata, which covers all the 

 upper range of the Catskill mountains, and many of the higher 

 tracts of the southern counties as far west as Steuben. In the 

 latter county it is only a thin mass of calcareous sandstone, and 

 farther west it thins out and disappears entirely; but in the Cats- 

 kill region it is probably 2,500 feet thick, and twice as much in 

 Pennsylvania; whence it is found southward along the mountain 

 ridges, but in thinner volume. 



The beds of this series are varied in color, being greenish gray 

 sandstones, fine-grained reddish sandstones, slates, shales, grind- 

 stone grits and an aocretionary mass appearing like fragments 

 of hard slate cemented in calcareous rock. The hard sandstone 

 often weathers in a peculiar way, dividing into thin layers almost 

 like piles of boards. ( ' 



The fossils of this rock are very few. Recent studies of this 

 group suggest that it is not entitled to distinct recognition but is 

 equivalent to the Chemung and perhaps to the Portage. Re- 

 mains of plants are numerous, forming occasionally tiny seams of 

 coal; and in some localities are teeth, bones and scales of fishes. 

 The latter are often conspicuous objects, as they are usually 

 white or bluish in color, and contrast strongly with the red rock. 



Life of the Devonian 



In the Devonian is observed a marked general advance in the 

 character of life- on the globe. 



iSponges were few. Brachiopods were varied and numerous. 

 Molilusks were abundant. Corals were highly developed and 



very numerous. 



Fishes were the dominant type and appear to have supplanted 

 the immense cephalopods which ruled in the Lower Silurian seas. 



Plant life was well represented on land, especially by ferns. 

 Conifers also existed. 



The abundant flora which gave rise to the coal formations of 

 the Carboniferous first became prominent in the Devonian. 



