486 
SILURIA. 
[Chap. XVIII. 
Lower Calciferous Group (4) ; while the Upper Calciferous (5) is only recognized 
in Newfoundland. 
u The Quebec Group (6, 7, 8) is divided into three parts, named from regions 
where they are largely displayed. The first or lowest division embraces the 
limestones and black slates of Point Levis, Orleans Island, and Phillipsburgh, 
with their numerous fauna of Trilobites and Graptolites, for the most part iden- 
tical with those of the Skiddaw Slates. The second or Lauzon division was at 
first united with the preceding, but has been separated from it on account of its 
great mineralogical importance and distinctness, it being the metalliferous zone 
of the Lower Silurian in North America. Magnesian rocks, including dolomites, 
magnesites, serpentines, diorites, and chloritic and steatitic beds, with micaceous 
and gneissic strata, characterize this Lauzon division, which is, moreover, rich in 
copper-ores, chiefly as interstratified cupriferous slates, and is accompanied by the 
ores of silver, gold, nickel, and chromium. The only fossils certainly recognized 
in it are an Obolella and two species of Lingula at its summit. It is overlain by 
the Sillery division, which consists of a great mass of sandstones and conglo- 
merates, 2000 feet thick, interstratified with red and green slates, and so far as 
yet known destitute of organic remains. 
u In a large part of its distribution, the Quebec Group is crystalline and meta- 
morphic j but the characteristic elements of the group are to be found both in 
the altered and unaltered portions. The Lauzon division, as lately shown 
by a careful investigation in the field by Sir William Logan, constitutes the 
Taconic range of hills in Massachusetts and New York, the strata of which 
are arranged in a synclinal form, and are traceable to a geological place between 
the Sillery of Berlin Mountain and the black graptolitic slates of Hoosick. The 
equivalency of the laconic system' of the late Professor Emmons and the 
Quebec Group has been completely established by the Geological Survey of 
Canada *. 
" In western Canada and New York there is a great palaeontological break 
between the Hudson-river and Clinton formations ; but in Anticosti, which is 
on the north-west side of the great St. Lawrence dislocation, and therefore in 
the western basin, the Hudson-river band is succeeded by a formation of 
limestone 306 feet in thickness, from which eighty-six species of fossils have been 
collected. Porty-one of these occur in the Hudson-river limestone, and 
eighteen pass upwards. Above this there occurs another formation of lime- 
stone 447 feet in thickness, with thirty-nine species, of which eighteen come 
from below and twenty-three pass upwards. The true Clinton beds succeed, 
crowded with Pentamerus oblongus. These beds of passage from the Lower 
Silurian in Anticosti, appear to correspond in horizon with the slightly fos- 
siliferous Oneida and Medina deposits of New York, and, together with the 
Clinton, Niagara, and Guelph deposits, which graduate into one another, they 
constitute a Middle Silurian group. In the eastern basin such beds of passage 
from the Lower Silurian are wanting ; and the only portion of the Middle Silu- 
rian series that has been met with there is a patch at the Forks of the Chatte 
River, whose horizon is about the base of the Clinton group. 
u In the western basin there is another great palaeontological gap between 
the Guelph formation and the Lower Helderberg Group. In it the Onondaga 
* Sir William Logan informs me that the same erroneously placed beneath all the Silurian rocks, 
series can be followed from the States of New is seen to rest upon the Potsdam Sandstone or 
York and Massachusetts throughout Vermont into ' Primordial ' Silurian. These facts prove the inap- 
Canada in three main undulations, bounded on plicability of the name ' Taconic ' to the oldest fos- 
the east by Upper Silurian and Devonian rocks, sil zone in Norway (see p. 353). 
On the west this series, which Dr. Emmons had 
