i62 The American Geologist. ^^''^h- ^^o^. 
of the water-lime group. But in all instances which I have 
known, where the Catenipora occurs in the isocalled water-lime 
group, there has been an extreme thinning out of the inferior 
groups, so that this one and the Hudson River group are 
brought within a short distance of each other." 
The above quotation shows that the presence of Halysites 
had much to do in leading Hall to conclude that the "Coralline 
limestone" holds the horizon of the Niagara. In 1843, how- 
ever, he does not make this correlation, but istates that its true 
position in the time scale is dependent upon the age of "the 
green shale containing iron pyrites." 
In 1852 Hall* makes a definite correlation with the Niagara 
limestone as follows : 
"I believe it can be conclusively shown that this coralline 
limestone is no other than the Niagara limestone, and indeed 
representing the entire Niagara group. In the first place, it 
holds the same position, being above the Clinton group [the 
inference here being that Hall correlates the green pyritiferous 
shale of the Schoharie section with the Clinton ; these shales, 
however, have yielded no fossils, and their age must be deter- 
mined from other sections] and below the Onondaga-salt 
group." The latter is again assumption, since the "Waterlime" 
of the Schoharie section is supposed to be the thinned eastern 
edge of the Salina. This "Waterlime," however, lies above 
the Coralline limestone, contains its fauna, but not a single 
species of Burypterus of the Waterlime farther west resting 
upon the Salina. Further, this "Waterlime" underlies the 
Tentaculite limestone or Manlius and should not be confused 
with the true Waterlime which underlies the Coralline lime- 
stone of Herkimer county. Hall was able to find the Niagara 
formation as far^east as Oneida county "where it has become 
very thin, and contains but a few fossils. * * * Over a 
part of Oneida county and the western part of Herkimer, 
there is a .space where no representative of the Niagara group 
has been traced continuously."' No one has found a Niagaran 
fauna east of Herkimer county or in the Helderberg moun- 
tains. The Coralline limestone, however, has been traced from 
Herkimer county to the southwestern side of the Helderberg 
mountains, and in this region it is, as Hall states, "more close- 
* Nat. Hist. N. V. Pal., ii, 1852, p. 321. 
