GEOGNOSY OF THE APPALACHIANS. 469 
between these two, and constituting, as it were, beds of passage 
between them. In this new formation were included the grapto- 
lites already described by Hall, and the numerous crustacea and 
brachiopoda described by Billings, all of which belong to the Levis 
slates and limestones. « To these and their associated rocks Sir 
William Logan then gave the name of the Quebec group, including, 
besides the fossiliferous Levis formation, a great mass of overlying 
slates, sandstones and magnesian limestones, hitherto without fos- 
sils, which have been named the Lauzon rocks, and the Sillery 
sandstones and shales, which he supposed to form the summit of 
the group, and which had afforded only an Obolella and two species 
of Lingula ;* the volume of the whole group being about 7000 feet. 
The paleontological evidence thus obtained by Billings and by 
Hall, both from near Quebec and in Vermont, led to the conclusion 
that the strata of these regions, so much resembling the upper 
members of the Champlain division, were really a great develop- 
ment, in a modified form, of some of its lower portions. Their 
apparent stratigraphical relations were explained by Logan by the 
supposition of “an overturned anticlinal fold, with a crack and a 
great dislocation running along the summit, by which the Quebec 
group is brought to overlie the Hudson River group. Sometimes 
it may overlie the overturned Utica formation, and in Vermont 
points of the overturned Trenton appear occasionally to emerge 
from beneath the overlap.” He, at the same time, declared that 
“from the physical structure alone, no person would suspect the 
break that must exist in the neighborhood of Quebec, and, without 
the evidence of fossils, every one would be authorized to deny it.” ¢ 
The rocks from western Vermont, which had furrlished to Hall 
the species of Olenellus, have long been known as the Red sand- 
rock, and as we have seen, were by Emmons, in 1842, referred to - 
the age of the Medina sandstone, a view which the late Professor 
Adams still maintained as late as 1847.{ In the mean time 
Emmons had, in 1855, declared this rock to represent the Cal- 
ciferous and Potsdam formations, the brown sandstones of Bur- 
lington and Charlotte, Vermont, being referred to the latter. § 
Billings, Paleozoic Fossils of Canada 
epikoa letter to Barrande, Amer. Jour. Boi., B xxxi, 218. The true date of this 
letter was December 31st, 1860, but, by a misprint, it is made 1831 
t+ Adams, Amer. Jour. Sci., II, v, 108 
§ Emmons, American Geology, II, 128. 
