SIXTH REPORT OF THE DIRECTOR I909 



99 



upward through passage beds into dolomite, the passage beds 

 were between it and limestone, which was, in turn, followed by 

 dolomite. This is the limestone from which Walcott obtained 

 the Saratogan fauna which he described. It seems to us to be a 

 calcareous phase of the lower portion of the dolomite formation. 

 We are proposing for it the name " Hoyt " limestone and regard 

 it as merely a local member of the dolomite. The name " Green- 

 field " limestone, given to it by Clarke and Schuchert, was pre- 

 occupied and must hence be replaced. 



At Saratoga also there is no trace whatever of the beds of the 

 four upper divisions of Brainerd and Seely's Beekmantown, B-E 

 inclusive; instead the limestone heretofore called Trenton rests 

 directly on the dolomite of division A. The Potsdam is thinner 

 than at Whitehall and Ticonderoga, the loss being from the base. 



Passing from Saratoga to the Mohawk valley the Potsdam 

 rapidly thins out to disappearance along with the passage beds, 

 letting the dolomite down on the Precambric. The dolomite 

 formation, however, remains substantially as before, and is over- 

 laid by the more calcareous formation which Vanuxem called the 

 " fucoidal " beds. For these we propose the name " Tribes Hill " 

 limestone, restricting the Little Falls dolomite to the beds 

 beneath. The one overlies the other unconformably. The Tribes 

 Hill thins westward and disappears west of Little Falls, letting 

 the overlying Lowville limestone down on the dolomite. 



The general section then, as we interpret it, is as follows : 



rUpper divisions of the Beekmantown ; un- 

 Beekmantown ^ named as yet 



I Tribes Hill limestone 



Unconformity 



Saratogan 



' Little Falls dolomite ; Hoyt limestone as a local 



basal phase 

 Theresa formation ; passage beds 

 Potsdam sandstone 



Historical 



It is not intended here to give an exhaustive resume of the 

 literature which deals wath the district, but merely to indicate 

 some of the more important papers. 



