. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 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 be
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 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. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of t
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