12 NEW YORK STATE MUSEUM 



name Pamelia formation is suggested by Professor Gushing for this 

 series. The invasion of the sea during this stage was from the west, 

 and this district marks the easternmost edge of its extent. Here 

 alone in the State is the formation well exposed. A name for the 

 New York expression of the series seems therefore called for. It 

 overlapped an old land surface, thins rapidly eastward and thickens 

 to the west, and its presence furnishes for the first time an adequate 

 explanation of the great thickness of limestone reported by the drill 

 in the deep wells of northwestern New York. 



On reaching the base of the Pamelia formation it was found to 

 rest everywhere on the beds which had been referred to as passage 

 beds during the work of the previous season, and to rest on them 

 with the most prominent unconformity noted among the sedimenta- 

 ries in riorthern New York. The basal beds of the Pamelia forma- 

 tion are weak and therefore seldom exposed but when seen show 

 everywhere a thin basal conglomerate and sandstone. The under- 

 lying formation had suffered considerable erosion as evinced by its 

 varying thickness and the varying thickness of the beds of the 

 Pamelia formation beneath the heavy fossiliferous limestone bed, 

 as shown in numerous sections in small areas. The time interval 

 in this unconformity seems to represent the whole, or the major 

 part of Beekmantown and Chazy time. Nothing that can be corre- 

 lated with the Beekmantown formation is represented in the section. 



For the so called passage beds beneath, the name Theresa forma- 

 tion is proposed, their entire thickness being well exposed in the 

 township of that name. This formation seems also to hold a fauna 

 not before noted in the State. 



The absence of the Beekmantown limestone, the great unconform- 

 ity between the Theresa and Pamelia formations, and the close con- 

 nection of the former with the Potsdam into which it grades, and 

 of the latter with the Lowville, seems to add weight to the view 

 previously urged, that the Potsdam-Beekmantown passage beds of 

 northern New York, with possibly a portion of the Beekmantown,' 

 are so closely connected with the Potsdam that they must of neces- 

 sity be Classed with them, and that, since the normal fauna of the 

 middle and upper Beekmantown is plainly a Lower Siluric fauna, 

 the line of division between the two great rock groups is to be found 

 somewhere within the limits of what has heretofore been considered 

 as Beekmantown. In this connection the discovery of an uncon- 

 formity between Brainerd and Seely's group A and group B of the 

 Beekmantown, made by Messrs Ruedemann and Ulrich in the Ticon- 

 deroga region the past summer, comes to have large significance. 



