RAYMOND: CORRELATIOX OF THE ORDOVICIAN STRATA. 



257 



above), and the Clitambonites bed (zone 6). The zone 7, with its 

 large gastropods, particularly the Fusispiras and Troehonemas, Cijclo- 

 spira bisulcata, Rafinesquina deltoidea, and Strophomena trilobata, is 

 an exact counterpart of the Picton of Ontario. 



The Clitambonites beds of both Ontario and Minnesota are char- 

 acterized by the same species of Clitambonites and Parastrophia, and 

 there are many more fossils common to the two. 



The Decorah shales of Minnesota have been correlated by Dr. 

 Ulrich with the strata above the Leray-Black River and below the 

 cystid beds at Kirkfield, Ontario, and on this point we are in agree- 

 ment. 



The Stewartville dolomite is not present in Ontario, nor have any 



NORTHERN 



DOLGEVILLE PAJTERSONVILLE 



ALBANY 



f(r. 



M/NN. 



ONT/IRIO ^ ^ TRENTON 

 FALLS 



CANflJOHARIE 



SCHENECTADY 



Fig. 1. — Correlation of the sandy and shaly strata of eastern New York witli the 

 calcareous strata of the more western localities. The strata represented by the 

 dots are predominantly sandy shales and sandstones, with subordinate amounts of 

 black shale. The next beds below are very fine-grained shales, usually very dark 

 in color, and the remaining strata, represented by the "brick" design, are prin- 

 cipally limestone. For Plat'ville, read Plattcville. 



of its characteristic fossils been found there. In Minnesota a part 

 of the Prosser fauna passes over into the Stewartville, and there does 

 not appear to have been any break in the sedimentary record, so that 

 there was apparently here a persistence of limestone deposition after 

 it had ceased in Ontario. 



Reviewing what has been said of the preceding sections, it will be 

 seen how the shales in their westward progress transgressed higher and 



