8. G. Williams — Mocks of Lower Ilelderberg Age. 139 



Aet. XIY. — The Westward Extension of Rocks of Lower Helder- 

 berg Age in New York ; by S. G. Williams. 



In a paper published in this Journal, September, 1885, it 

 was shown that the extensive plaster beds of Cayuga County, 

 near Union Springs, are associated with limestones both above 

 and below them, containing fossils of the Water-lime Group 

 and of some of the lower stages of the Lower Helderberg, like 

 Eurypterus remipes, Leperditia alta, Nucleospira veniricosa, Meris- 

 tella bisulcata and Spirifera Vanuxemi, and hence it was in- 

 ferred that their geological position is as high as the summit of 

 the Water-lime Group, rather than in the Salina, as they have 

 heretofore been thought to be. 



I wish now to return to the subject to show that the Lower 

 Helderberg period, including all above the Water-lime Group, 

 is represented at least as far west as Cayuga Lake, by lime- 

 stones not less than sixty-five feet in thickness, containing an 

 unmistakable Lower Helderberg fauna; as well as to compare 

 with this series of rocks the results of some examination of 

 strata of similar geological position on the outlet of Skaneateles 

 Lake and at Oriskany Falls. 



The rock series in Cayuga County which is interposed be- 

 tween the gypsum beds and the Oriskany sandstone consists of 

 from sixty-five to seventy feet of impure limestones, partly of 

 a drab color, and partly blue which mostly weather drab. 

 Fossils are quite rare in these rocks, and from this fact, coupled 

 with their usual drab color on weathering, and their proximity 

 to the plaster beds which were assigned to the Salina period, 

 they have hitherto been thought to belong to the Water-lime 

 Group, while the Lower Helderberg proper has been thought 

 to be unrepresented west of Oneida County. Thus Vanuxem, 

 p. 123 of his Report on the 3d District of New York, says that 

 the immediate associates of the Oriskany sandstone cease be- 

 fore reaching Cayuga Lake, and that the Oriskany rests on the 

 Manlius Water-lime ; and Professor Hall says, Paleontology 

 of New York, vol. iii, p. 37, that the Lower Helderberg, from 

 which he excludes the Water-lime, making the Tentaculite its 

 base, is scarcely known west of Oneida County. In the final 

 reports of the 3d and 4th districts, however, the Tentaculite 

 limestone is included in the Water-lime Group, the fossils 

 which are figured as belonging to it are chiefly those which 

 characterize the Tentaculite limestone, and several of these are 

 mentioned by Prof. Hall as occurring at a single locality in 

 Ontario County. 



Now rare as fossils are in the strata under consideration in 

 Cayuga County, careful search has brought to light a number 



