of Lower Helderberg Age in New York. 143 



These gray beds are also, as Vanuxem remarked, dissimilar in 

 physical character to the Shaly Lime of Schoharie County, 

 and, though gray and somewhat crystalline, bear no great re- 

 semblance to the rough Pentamerus limestones of the eastern 

 localities. 



Below these gray beds, the limestones for about ninety feet 

 are of a prevailing blue color, and, with an exception presently 

 to be mentioned, are so pure as to be very largely quarried for 

 lime-burning and for a flux in the iron furnaces a few miles 

 north near Clinton. For twenty-nine feet below the gray beds, 

 these blue limestones show but few fossils save Favosites Helder- 

 bergice and Stromaiopora which are tolerably abundant. Below 

 these occur about seven feet of impure, slightly magnesian, 

 grayish beds, often highly laminated and occasionally present- 

 ing beautiful ripple-marks, testifying to a considerable tempo- 

 rary change in the conditions of deposition. The impurities 

 in these beds, amounting to 20 per cent of insoluble matter 

 chiefly siliceous, render them unfit for lime-burning, and they 

 are used for building stone. Though not remarkably rich in 

 fossils, many of the slabs show fine large pygidia of Dahnania 

 pleuroptyx and occasional Distinct discus, and I observed one 

 large slab which, besides several individuals each of these two 

 species, had also a beautiful Conularia unlike those described in 

 vol. iii, Paleontology of New York. Dalmania pleuroptyx con- 

 tinues for several feet below the building stone beds, from 

 which point downward for about forty-five feet few fossils are 

 seen save Stromaiopora, Favosites Helderbergioe, Strophodonta 

 varistriata, and rarely Spirifera Vanuxemi. Euomphalus sinu- 

 atus has also been given me as from these beds. Near the base 

 of the 115 feet of strata which 1 measured, Stromatopora is 

 found very abundantly associated with S. varistriata in thin- 

 bedded limestones. In beds a little below my measured sec- 

 tion, reached by going northward along the banks of the aban- 

 doned canal, since its waters flow northward while the strata 

 all dip gently south, Spirifera Vanuxemi and Leperditia alta are 

 found in great abundance with a few Spirorbis laxus and 

 Choeteies fructicosus, while an occasional thin layer abounds in 

 the Tentaculite which occurs in such myriads at a like horizon 

 in the eastern localities. 



The lower strata of the series for nearly fifty feet contain, 

 therefore, apparently only fossils which are found commonly 

 in the Tentaculite limestone, and they doubtless correspond 

 well with that stage. Possibly also the very uppermost beds, 

 unlike as they are in physical character to the Shaly Limestone 

 of the eastern counties, may be parallel with that horizon ; but 

 from the complete intermingling of forms characterizing the 

 Lower Pentamerus and the Shaly Limestone in fully fifty feet 



