1184 



NEW YORK STATE MUSEUM 



5 Hard black cement, 4 feet 8 inches thick, is much like 4, but 

 it is somewhat harder, breaks with a more conchoidal fracture, 

 and it often has irregular dark blotches on an olive-gray ground. 



Cobleskill 



5a The middle ledge is a 7 inch band of somewhat shaly 

 slightly more calcareous limestone that can usually be separated 

 from the top of the hard black cement as a distinct bed. This 

 band is highly fossiliferous, but the fossils can scarcely be seen 

 in the fresh rock, and they appear best after the rock has been 

 burned in the kilns. A large species of Leperditia is abundant, 

 and Orthothetes hydraulic us and Ehynchonella 

 1 a m e 1 1 a t a are present. This middle ledge of the Vlightberg 

 is, as demonstrated by Hartnagel, the attenuated eastern exten- 

 sion of the Cobleskill limestone of the Schoharie section. 



Rcmdout beds 



Comprising the light cements 



6 Hard gray cement, 5 feet thick, is a solid bed which on cross 

 section shows horizontal bands of olive-green on a lighter gray 

 ground. The rock has a splintery fracture; is of very fine grain 

 at top and center, and at bottom is quite coarse. 



7 Soft gray cement, 3 feet 3 inches thick, has a more even tone 

 of slightly darker gray than 6, and is of finer grain and more 

 conchoidal fracture. 



8 The " curly " is a 19 inch band of dark gray, fine grain 

 cement rock with undulating lamination, which is usually much 

 sheared and crushed to a dark powdery mass by lateral move- 

 ment of the overlying formations. 



It is to be noted that in general the lower part of each 

 cement layer is of coarser grain than the upper part, except in the 

 hard black cement which is a smooth stone throughout. Some 

 quartz sand is found in all the layers excepting the hard black. 

 It occurs in the form of well rounded minute grains of limpid 

 quartz scattered irregularly through the limestone, and from its 

 resemblance to the wind-blown sand of deserts, it may be consid- 

 ered to have been brought by the wind from some near-by arid 

 lands which bordered or inclosed the mud flats of Nedntaric 

 time. 



