8 NEW YORK STATE MUSEUM 



appearance identical with the lower Cambric conglomerate lime- 

 stone of Tvoy ami contains 11 y o 1 i t h e 1 l^n s m i <• a ii s 

 Billings, a chanicteristic fossil of that locality. 



2 l*ebbles of nonfo»siliferous grayish and reddish sandstones 

 which may repi*esent in age the Potsdam sandstone or Beekman- 

 town limestone beds, or may be derived from sandstone beds in 

 the underlying Normans kill graptolite shale. They are the 

 strongly prevailing clas6 of pebbles at Schodack Landing, have 

 diminic^hed in number at the Moordener kill, though still out- 

 numbering the limestone i>ebbles, and are greatly reduced in 

 relative quantity farther north, on Kysedorph hill. 



3 Pebbles of a black, hard limee^tone, which appeai-s crystal- 

 line by the pi-ofuse admixture of crystallized cystid plates. This 

 class, which is rei>resented by only a few pebbles found on Kyse- 

 dorph hill, is similar in lithologic apix^arance to the Chazy lime- 

 stone as exjK>sed near Valcour on Lake Champlain. It has been 

 found to contain B o 1 b o p o r i t e s a m e r i c a n u s Billings, a 

 characteristic Chazy fossil (see p. 11) and P a 1 e o c y s t i t e s 

 t e u u i r a d i a t u s Hall. 



4 The Lowville limestone is represented by hard, bluish gray 

 pebbles with numerous birdseyes, P h y t o p s i s t u b u 1 o s a 

 Hall, which differ in nothing from the Lowville limestone beds 

 as exposed along the Mohawk and Black river valleys. At the 

 Moordener kill also T e t r a d i u m c e 1 1 u 1 o s u ni Hall sp., a 

 characteristic fossil of the Lowville limestone, has been collected. 

 The pebbles of this group, thougli not jaevailing in any of the 

 localities, arc the most striking by their color, and in size they 

 far surpass all others. At. If^chodack Lauding boulders of a foot 

 and a half iu diameter have been observed. Oj^posite the rail- 

 road .station, in the conglomerate of the rocky wall behind the 

 village, they can be noticed from the car windows. At the Moor- 

 dener kill boulders a foot in diameter occur. Their large size is 

 evidently due to their great hardness, for their relatively small 

 number and strongly water worn rounded surface indicate their 

 derivation from a more distant place. On Kysedorph hill only a 

 few small pebbles were found. 



