242 New York State Museum 



speciosa, Plcthopeltis saratogensis etc. (respectively, Dicel- 

 locephalus, Ptychaspis and Agraulos). Trilobites, gas- 

 tropods and Lingulepis acuminata occur at many horizons. 

 The Hoyt formation has been found at several localities 

 in Saratoga and Washington counties, and the fauna of 

 this horizon has been found in the Wappinger terrane of 

 southeastern New York (Dutchess and Orange counties). 

 The Little Falls dolomite (Clarke '03) was named from 

 the type locality at the pass in the Mohawk valley at 

 Little Falls, Herkimer county. It was previously placed 

 in the Beekmantown formation and therefore considered 

 as Lower Ordovician (—Canadian), but later studies 

 have shown it to be the uppermost member of the Lower 

 Ozarkian series in New York State and to be separated 

 from the rocks of the Canadian system above by an un- 

 conformity. This formation is a light gray to dark gray 

 crystalline or subcrystalline dolomite. Black and gray 

 cherts are found frequently at certain horizons, and cer- 

 tain layers are full of nodules of crystalline calcite. The 

 summit is very apt to be formed of a massive Cryptozoon 

 reef, often heavily silicified. The maximum thickness of 

 this formation is about 200 feet. Except for the Crypto- 

 zoon, fossils are very scarce. This formation occurs with 

 the rest of the Ozarkian series at the east and south of 

 the Adirondack area, but continues farther to the west 

 in the Mohawk valley, extending beyond Tribes Hill to 

 Little Falls and Newport and, because of the absence of 

 the other beds, resting upon the Precambrian. The 

 Potsdam shore must have had a more southerly trend in 

 this area, that is, the Little Falls subsidence covered more 

 of the southern part of the old land area than the Pots- 



