Review of the New York Geological Reports. 357 



aspect ; and since it crops out three hundred feet below beds of 

 fossiliferous limestone, known to be the equivalent of the Tren- 

 ton limestone of New York, there is a great probability of the 

 identity of the two rocks ; still the palaeontological evidence is 

 wanting, since the Wisconsin sandstone has not yet yielded any 

 fossils. From the reports on Michigan this formation seems to 

 exist on Lake Superior. 



At its junction with the overlying calciferous sandrock the 

 Potsdam sandstone puts on a variety of aspects ; sometimes it is 

 a calcareous breccia, sometimes a dark brown iron mass, in band 

 specimens resembling a graywacke ; and again a dark slaty sand- 

 stone with impressions of fucoids. "At the Falls of Montmo- 

 renci, this rock is stained with carbonate of copper, which gives 

 it the aspect of one of the varieties of new red sandstone." (Em- 

 mons's Report, p. 103.) 



The typical mass, which gives name to the rock, occurs at the 

 Potsdam quarries, on the De Grasse River, St. Lawrence Co. 

 They furnish the most valuable building stone in the state ; in- 

 deed, Prof. E. maintains that few materials could compete with 

 it, if situated near a market, on account of its being so perfectly 

 workable and manageable, and at the same time so even-bedded. 



Calciferous Sandrock.-— (No. 2 of Pennsylvania and Virginia 

 Reports.) The predominating rock of this formation is, as the 

 name denotes, a sandy limestone. It has usually a fine crystal- 

 line structure, intermixed with earthy matter and small masses of 

 of calcareous spar. It consists, according to Emmons, of the fol- 

 lowing divisions : Fucoidal layers, calciferous sandrock, drab- 

 colored layers, or water limestone, cherty beds, geodiferous strata 

 filled with a species of Orthis, encrinital beds, mass containing 

 Bellerophon and other univalves, oolitic layers ; in all attaining a 

 thickness of between two hundred and fifty and three hundred 

 ^et. Sometimes the entire mass is absent. 



Fossils are both rare and obscure in this formation. Those 

 which have been observed and are confined to this rock are rep- 

 resented on the succeeding page. 



Plate 2, fig. 1, Ophileta levata. Fig. 2, O. complanata. 



Encrimte 



u Pper part of the calciferous sandrock at Chazy. 



4 



ceras primigenium. 



V °l- xlvii, No. 2.— July-Sept. 1844. 



46 



