3G8 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



The courses of the Waterlime rocks (which are the lower) are 

 thin, and often not more than half an inch thick. They ring under 

 the hammer. The limestone is brownish and geodiferous, impure, 

 from the presence of silex, and often without the power of cementing 

 (Mather, Report, p. 349). 



The lowest and middle parts of the Tentaculite-limestone are slaty 

 and black. The upper portion is black and dark grey, compact, and, 

 in some layers, subcrystalline. 



Transition. — The plane of separation between the Waterlime 

 group and the Onondaga-Salt is rather well defined on the east side 

 of New York (Mather, p. 348). At the foot of the Helderberg 

 Mountains, the Waterlime group rests on Oneida Conglomerate, there 

 called Shawangunk Grit, having however, but only in places, some 

 pyritous strata, red shales, and grits between them, altogether usually 

 under 30 feet in thickness. The pyrites is sometimes found in the 

 limestone, and sometimes in the conglomerate, but often also only in 

 the intervening shales and grits. 



This is an indication of slow transition. The groups Onondaga- 

 Salt, Niagara, Clinton, and Medina do not appear here. 



Place. — This group is coexistent with the Lower Helderberg divi- 

 sion, and is well seen in Hurley, Kingston, Marbletown, Rochester, 

 Saugerties, Catskill, Athens, Coxsackie, and New Baltimore counties, 

 on the west side of the Hudson River. 



Thickness. — 30 feet at Schoharie, and 100-150 feet elsewhere. 



Position. — In Kingston, Marbletown, Saugerties, and New Balti- 

 more, this group is well exposed by subterranean disturbances which 

 have raised it at various angles and in different directions ; but from 

 Coeymans, by Bethlehem, Berne, &c. towards Central New York, the 

 rock dips gently to the west and south, cropping-out towards the 

 Hudson and Mohawk Valleys with a mural escarpment or steep 

 acclivity. 



Fossils. — Mather found them to be few ; and these few have not 

 yet received proper attention. 



The lowest part of the Tentaculite Limestone abounds in Favo- 

 sites, Columnaria, Catenipora, &c. The middle possesses Tentacu- 

 lites ornatus, Leperditia alta, Orthis plicala, Avicula rugosa (all 

 typical, Hall) . The upper part furnishes several species of Asaphus 

 and Calymene. 



Prof. H. D. Rogers*, speaking of the Lower Helderberg Limestones 

 of New York, of which Waterlime is the oldest, says that many of 

 their fossils are generically and even specifically identical with the 

 shells, corals, trilobites, and other fossils of the Wenlock of Great 

 Britain, and therefore its nearest equivalent in America ; and that 

 it is the uppermost deposit of the Appalachian Sea (i. e. the Lower 

 Helderberg group) . This is the general conviction of geologists. 



In 1854, James Hall, while employed in his great work on the 

 Palaeozoic Fossils of New York, said (Sill. Journ. xvii. n. s. p. 312) 

 that, " poor as our lists now are, in the Lower Helderberg group, I 



* Johnston's Physical Atlas, new edit. 



