38 NEW YORK STATE MUSEUM 



Rondout waterlime 



The preceding formation begins the series which represents the 

 Manhus group. The deposition of waterlimes continues and the 

 Rondout division is composed of a thickness of about 40 feet of 

 hard, dark, bhie gray dolomitic Hmestone weathering to a light drab, 

 in layers of from 6 inches to 2 feet in thickness, some of which, in 

 the upper part, are highly straticulate in appearance on account of 

 thin seams of waterlime at intervals of J4 to i inch. In some near-by 

 exposures the lower part is more or less brecciated and contains 

 many irregular cavities of which a large proportion was caused by 

 the dissolution of the little coral Cyathophyllum hydrau- 

 lic u m Simpson. These beds are exposed but slightly in this 

 quadrangle in the vicinity of the Dunlop limekiln, ij4 rniles north 

 of Jamesville; in the bottom of the cliff at White lake, lyz miles 

 northeast of Jamesville and in a deep ravine in the northeast corner 

 of this quadrangle. It is more favorably exposed in many places 

 in the vicinity of Manlins. The fossils Cyathophyllum 

 h y d r a u 1 i c u m Simpson and Leperditia alta, together 

 with Spirifer vanuxemi are common and characteristic of 



the horizon. 



Manlins limestone 



Very dark blue black, when fresh weathering to a light bluish 

 gray, and after Ibng exposure having a straticulate appearance pro- 

 duced by thin seams of impure limestone or waterlime at intervals 

 of 54 to 2 inches or more. This rock attains a total thickness of not 

 less than 74 feet and occurs mostly in even layers from 6 inches 

 to 2 feet in thickness_, which split easily along lines of deposi- 

 tion, and some layers have a smooth cross or " diamond " fracture. 

 It is very hard but rather brittle. At the top this formation includes 

 two layers of impure dolomitic limestone extensively quarried in 

 this vicinity for cement. At Jamesville the lower layer is 4 feet, 6 

 inches thick and increases slightly toward the west, while the upper 

 is 3 feet, 6 inches thick and decreases _in that direction- These 

 are separated by 2 feet, 11 inches of dark laminated " diamond rock," 

 the quarryman's term for the rock above described. The cement 

 rock is lighter colored and more compact, showing but faint lines 



