8 NEW YORK STATE MUSEUM 



appearance identical with the lower Cambric conglomerate lime- 

 stone of Troy and contains H y o 1 i t h e 1 1 u s m i c a n s 

 Billings, a characteristic fossil of that locality. 



2 Pebbles of nonfossiliferous grayish and reddish sandstones 

 which may represent in age the Potsdam sandstone or Beekman- 

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

 the underlying Normans kill graptolite shale. They aire the 

 strongly prevailing class of pebbles at Schodack Landing, have 

 diminished in number at the Moordener kill, though still out- 

 numbering the limestone pebbles, and are greatly reduced in 

 relative quantity farther north, on Rysedorph hill. 



3 Pebbles of a black, hard limestone, which appears crystal- 

 line by the profuse admixture of crystallized cystid plates. This 

 class, which is represented by only a few pebbles found on Eyse- 

 dorph hill, is .similar in lithologic appearance to the Chazy lime- 

 stone as exposed near Valcour on Lake Champlain. It has been 

 found to contain Bolbopo rites a m e r i c a n u s Billings, a 

 characteristic Chazy fossil (see p. 11) and Paleocystites 

 tenuiradiatus Hall. 



4 The Lowville limestone is represented by hard, bluish gray 

 pebbles with numerous birdseyes,, Phytopsis tubulosa 

 Hall, which differ in nothing from the Lowville limestone beds 

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

 Moordener kill also Tet radium cellulosum Hall sp., a 

 characteristic fossil of the Lowville limestone, has been collected. 

 The pebbles of this group, though not prevailing in any of the 

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

 far surpass all others. At Schodack Landing boulders of a foot 

 and a half in diameter have been observed. 'Opposite 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 Rysedorph hill only a 

 few small pebbles were found. 



