Il6 NEW YORK STATE MUSEUM 



sociated with' the Hoyt. Beds iy to 24 of the Ticonderoga section 

 are thought to represent the same horizon. Walcott reports L i n - 

 g u 1 e p s i s acuminata in the passage beds. All the upper 

 portion of the section has the typical characters of the middle and 

 upper parts of the Little Falls dolomite^ but unfortunately the 

 summit is not quite reached. Loose chert, apparently from the 

 upper part of the dolomite, found 2 miles northeast of Whitehall, 

 contains two gastropods and a cephalopod that mark the middle part 

 of the Ozarkic in Missouri. The same beds there contain trilo- 

 bites closely allied to those found in the Hoyt limestone near 

 Saratoga. 



In the National Museum is a small collection of fossils made by 

 Walcott from 2 miles north-northeast of Whitehall which contains 

 a half dozen specimens of the fauna of division D and demonstrates 

 the presence of at least that member of the Beekmantown. Since 

 Whitehall is due south of Ticonderoga and much nearer that point 

 than Saratoga, it is quite likely that other members of the Beek- 

 mantown were deposited in this region. 



Mohmvk valley sections 



Passing southward from Saratoga to the valley exposures the 

 Potsdam sandstone rapidly thins and disappears, letting the 

 passage beds and then the Little Falls dolomite down on the 

 Precambric. The manner of disappearance seems to us to in- 

 dicate plainly that the Potsdam vanishes because of overlap, 

 and that the dolomite of the valley is the direct equivalent of 

 that of the Saratoga and Ticonderoga sections and wholly above 

 the Potsdam. The paleontological evidence, so far as it goes, con- 

 firms this belief. 



In the most easterly of the Mohawk valley sections a lime- 

 stone formation of considerable thickness, the " fucoidal layers " 

 of Vanuxem, overlies the dolomite. This limestone is thickest 

 at the east and thins westward to complete disappearance west 

 of Little Falls. The published sections of Prosser and of Cle- 

 land, with the faunal studies of the latter, left no doubt of the 

 fact of the general persistence and equivalence of both the dolo- 

 mite and limestone formations throughout the valley, hence our 

 comparative study seemed to call for sections only at the east 

 and west ends respectively. We measured and studied sections 

 at Tribes Hill and Cranesville at the east, and at Little Falls, 

 Middleville and Newport at the west. 



