COMPARISON OF SECTIONS 175 



to Ctunings, they have a thickness of 250 feet at Cranes village, two 

 miles below Amsterdam and about 37 miles down the river from Little 

 Falls. At Little Palls their thickness is only a few feet, so that they 

 apparently thin rapidly westward. At the t}^e locality of the Little 

 Falls dolomite, therefore, these layers barely appear, while down the 

 river they attain considerable thickness. At several localities Lingulella 

 acuminata and Ophileta complanata are reported from the formation, 

 and Ctunings reports in addition two species of undetermined lamelli- 

 branchs. Hall figures a few other forms in volume 1 of the Paleontol- 

 ogj. This fauna seems to the writer to indicate a probable equivalence 

 of these fucoidal laj'ers with the Theresa formation and Division A, or at 

 least that they are no older. If this be correct, then either the bulk of 

 the Little Falls dolomite is of substantially the same age or else there is 

 an undiscovered unconformity between it and the "fucoidal layers." 

 Until search has been made for evidence of such a break and until the 

 fauna of the fucoidal layers is better Imown, the precise age of this for- 

 mation must remain uncertain. 



Conclusion 



It has been shown that four formations — the Lowville, Pamelia, 

 Theresa, and Potsdam — are present underneath the Black Eiver lime- 

 stone in the Watertown region, and that there is a great unconformity, 

 both by erosion and by overlap, between the Theresa and Pamelia forma- 

 tions. The Pamelia formation is of upper Stones Eiver age, and thus a 

 formation hitherto unrecognized in the New York section. It is thought 

 that the unconformity mentioned can be traced down the Saint Law- 

 rence valley to the Champlain meridian and represents the expanded 

 western representative of the break discovered by Ulrich in the Cham- 

 plain valley between Divisions A and B of the Beekmantown. It is also 

 thought that it represents the proper line of division for northern New 

 York between the Cambrian and Lower Silurian systems, thus relegating 

 to the Cambrian nearly 400 feet of strata which have hitherto been 

 classed as Beekmantown. As thus restricted, the New York Beekman- 

 town had much the same distribution as the succeeding Chazy, being laid 

 down in an eastern basin, from which an arm projected westward up the 

 Saint Lawrence trough, while the remainder of the state was mostly or 

 entirely above sealevel. 



The writer has recently discussed the early Paleozoic oscillations of 

 level in northern New York, as indicated by the evidence in hand at the 



