of Lower Helderberg Age in Neio York. 141 



theless, to learn that the circumstances which favored the depo- 

 sition of a series of limestones of diverse physical characters 

 with a rich and varied fauna in Eastern New York during the 

 Lower Helderberg period, were not wholly interrupted farther 

 westward, as has been supposed, at the close of the Water- 

 lime epoch; but continued in a modified form and under sim- 

 pler and more uniform conditions possibly to its very close, 

 marked by the prevalence only of a few of the hardier and 

 more persistent forms of life. 



The limestones which underlie the Oriskany sandstone on the 

 outlet of Skaneateles Lake, about fifteen miles east of the region 

 just described show an exposure so far as they are laid open by 

 quarries, of thirty-five feet, but Mr. E. B. Knapp, a careful local 

 geologist, judges their entire thickness to be more than double 

 this. Any attempts at inferring the thickness of these beds with- 

 out actual measurement is, however, liable to errors, since the 

 local disturbances which were noted in my paper on the age of 

 the gypsum deposits as affecting the corresponding strata on 

 Cayuga Lake, occur here also, the extensive quarries revealing a 

 synclinal bend of a few degrees dip, and with an east and west 

 strike. The beds which admit of definite measurement consist, in 

 ascending order, of nine feet of bluish limestone well supplied 

 with Strophodonla varistriala and Spirifera Vanuxemi ; from ten 

 to eleven feet of dark drab beds in three seams which are 

 largely burned for hydraulic lime; three feet and a half of blue 

 limestone which is highly esteemed for quicklime ; and twelve 

 feet of blue limestone of highly variable and often siliceous 

 character. Immediately beneath the Oriskany sandstone the 

 upper member of the series is replete with Stromatopora and 

 Leperdita. alta, and contains besides, Spirorbis laxus, somewhat 

 abundant and beautifully preserved Holopea (Littorina) antiqua, 

 and occasional Favosites Belderbergiaz. 1 have observed also 

 with these a single example of Spirifera Vanuxemi, although 

 Mr. Knapp assures me that it rarely occurs above the Hydraulic 

 lime. The small series of fossils here enumerated, as well those 

 prevailing below the hydraulic beds as those which are found 

 above, certainly indicates the horizon of the Tentaculite Lime- 

 stone as it occurs in the eastern part of the State ; and the sim- 

 ilarity to that group is strengthened by the occurrence at its 

 summit of a bed of Stromatopora, recalling the " thin mass of 

 limestone consisting almost entirely of the coral Stromatopora, 

 and constituting a very persistent member of the group," 

 which Professor Hall gives, p. 37, vol iii, of New York Paleon- 

 tology, as the uppermost member of this limestone in the east 

 Whether however this fact indicates that strata synchronous 

 with the higher members of the Lower Helderberg series were 

 never deposited in this region, where the limestones are sue- 



