530 NEW YORK STATE MUSEUM 



Potsdam to the dolomite of the Beekmantown in southern Can- 

 ada, and concludes from examination of the stratigraphic and 

 physical evidence that the Potsdam should be considered 

 the base of the Siluric system, instead of the uppermost mem- 

 ber of the Cambric. More recently the reports by Cushing on 

 the geology of Clinton county have contained some interesting 

 descriptions of the physical characters of the Potsdam sand- 

 stone at several localities on the northeastern slope of the 

 Adirondacks. The reports on the geology of the eastern flanks 

 of the mountains along the shore of Lake Champlain afford 

 little more than descriptions of the areal distribution of the 

 sandstone. 



Some descriptions of fossils found in the formation have been 

 published, in nearly all cases however without reference to the 

 particular horizons within the formation from which they were 

 obtained. Walcott's sections are the only descriptions extant 

 in which the fossils are referred to definite horizons in the 

 sections. 



The above statements will indicate that up to the present 

 time no systematic attempt has been made to study the forma- 

 tion in its entiretv throughout its distribution round the west- 

 ern, northern and eastern slopes of the Adirondacks and as a 

 result the following questions remain entirely or in great part 

 unanswered. 



1 What are the relations of the Potsdam to the subjacent 

 formations, whether the latter be of pre-Cambric or lower Cam- 

 bric age? 



2 What are the relations of the Potsdam to the superjacent 

 beds of the lower Champlainic (Siluric) series? 



3 Where shall the upper limit of the Potsdam be drawn? 



4 What are the physical characters that may serve as a 

 means of distinguishing the lower from the middle and upper 

 portions of the Potsdam sandstone? 



5 What are the fossil contents of the Potsdam and may they 

 be grouped to form distinct biologic zones? To what extent 

 are they reliable as a means of subdividing the formation and. 

 recognizing the lower, middle and upper portions? 



