BIGSBY PALAEOZOIC ROCKS OF NEW YORK. 393 



Along the Genesee River, and in Steuben County, the Catskill 

 group exhibits a thin mass of calcareous sandstone, highly charged 

 with iron, and containing the remains of fishes. It rises from beneath 

 the coal-measures of Pennsylvania, extending north, and resting on 

 the rocks of the Chemung group ; as in England it does on the 

 Ludlow formation (Hall, Rep. p. 278). 



Oblique laminae of deposition are often strongly marked. The 

 ripple-marks are common and good, the current going from N. 30° E. 

 to S. 30° W. (Mather, Rep. p. 313). 



Transition. — There is no well-marked line of demarcation between 

 the Chemung and Catskill groups. The change takes place gradually 

 by the diminution and final disappearance of the fossils found in the 

 former groups, and by the supervention of a harder and more solid 

 rock (Yanux. Rep. p. 187). Neither is there a defined plane of 

 separation between the Chemung rocks and the sandstones of 

 Ohio and Indiana which contain Carboniferous fossils (Hall, Am. 

 Journ. of Science, n. s., vii. p. 45). 



The Catskill group is the immediate predecessor, and the base, 

 therefore, of the Coal-formation (Vanux. Rep. p. 189). 



From lithological reasons alone, the two deposits Chemung and 

 Catskill are not synchronous. The olive-shales and sandstones of 

 Chemung, full of Strophomence, Spiriferi, and Atrypce, are succeeded 

 by a red sandstone destitute of the organic remains of the lower 

 rocks. In the higher rocks, shells are few and new, and everywhere 

 there are Fish. 



Place. — In his district, Vanuxem finds this group in the Counties 

 of Otsego, Chenango, Broome, Steuben, and Tioga. Hall states that 

 it occupies all the County of Delaware, and portions of the Counties 

 of Sullivan, Ulster, Greene, Schoharie, and Albany ; but its main 

 body lies in the Catskill Mountains (Hall, Rep. p. 278). 



In the five first-named counties, Catskill being the terminal group 

 of the New York series, it holds the highest position relatively to 

 the other rocks, and caps some of the greatest elevations. 



Position. — The Catskill group is conformable with the Chemung. 

 Although its strata in the Catskill Mountains seem to the eye to be 

 horizontal when viewed near, they are not so really, but dip at a 

 slight angle to the south-west. From Caterskill Creek the layers 

 emerge in a succession of terraces, with a steep bold escarpment on 

 the east, sloping away gradually to the west (Mather, Rep. p. 306). 



The directions of the main axes of elevation and depression are 

 from N.N.E. to S.S.W., and from E.S.E. to W.N.W. ; and they have 

 two systems of smooth joints corresponding with and parallel to 

 them. 



Thickness. — It varies from 2000 feet in Pennsylvania to 4000 feet 

 in the Catskill Mountains (Mather, p. 306), with a rapid diminution 

 of thickness from the aforesaid mountains westwards (Hall, Rep. 

 p. 278). 



Fossils. — Plants very abundant, terrestrial and marine, resembling 

 those of Ithaca and Chemung, but more numerous. There are thin 

 seams of coal, with Sigillaria simplicita and Fucoids in the red 



