LOWER SILURIC SHALES OF THE MOHAWK VALLEY 53 



Sphenophycus latifolius was observed only 180 feet 

 below the Manlius limestone. Since we have not observed this fossil 

 in the Indian Ladder beds and consider it as characterizing the Sche- 

 nectady formation, it would follow that the Indian Ladder beds are 

 here already reduced to less than 200 feet in thickness. The orange 

 colored rusty limestone bands of the lower Indian Ladder forma- 

 tion were in this section observed at several places above the 

 Sphenophycus beds. 



Westward between Altamont and Schoharie the uppermost part 

 of the Lower Siluric is nearly everywhere found buried under drift. 

 In the road-ditch halfway between East and West Township the 

 characteristic orange colored limestone was observed only 10 feet 

 below a ledge of Manlius limestone. 



To the east of the Indian Ladder the only opportunity for the 

 observation of the Indian Ladder beds is afforded by the New 

 Salem sections described by Prosser and Rowe (title 34, page 334). 

 The authors describe there two sections, one the Countryman Hill 

 section, and another south of New Salem. In the former section 

 57 feet of " bluish gray, fairly massive sandstones which alternate 

 with dark colored argillaceous shales," are cited as representing the 

 Lower Siluric. These are separated by a covered interval of 10 

 feet from the Manlius limestone. In the other section, which is but 

 half a mile to the east, the contact between the Lower Siluric and 

 the overlying beds is shown. Prosser and Rowe describe the lower 

 part of the sections as follows (op. cit. page 338) : 



Feet 



B4 Thin bedded dark blue limestone. Tentaculite 



limestone 32 1/2 



33 Drab, impure limestone, well exposed in the run 



at the foot of the cliff. Waterlime 61/2 



B2 Greenish sandstone to coarse arenaceous shale 

 containing plenty of iron pyrites, 10 inches in 

 thickness. Possibly it represents the attenu- 

 ated Clinton formation 1/2 



Bi Dark blue to olive tinted argillaceous shales well 

 exposed in the steep banks of the brook. 

 Hudson River shales. 90 



A third outcrop of the Lower Siluric shales is found between 

 these two in the culvert and ravine just south of New Salem at the 

 new State road. Here about 20 feet of dark shales with a few 

 sandy layers are exposed, which extend within 15 feet from the 

 Manlius (Tentaculite) limestone. 



