148 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [ Dec. i; 
latest views on this subject which I have met with are those given by 
Mr. James Hall in the Report on the Geology of the 4th district of 
New York, p. 15 and p. 517; and they approach very nearly the 
conclusions to which I have been brought by the examination of the 
fossils. 
Mr. Hall’s tables are as follows ; beginning with the lowest beds. 
New York System. 
Equivalent in Great 
Geographical 
Britain. 
Tp is Geological subdivisions. 
{ Potsdam sandstone. 
Calciferous sandrock. 
Chazy limestone. 
Bird’s-eye and Black-river limestone. 
Champlain division. { Trenton limestone. 
Utica slate. 
Hudson River group. 
Grey sandstone. 
| Oneida conglomerate. 
Medina sandstone. 
Ontario division. jon group. 
Niagara group. 
{ Onondaga salt group. 
Water-lime group. 
Pentamerus limestone. 
Delthyris shaly limestone. 
Encrina] limestone. 
Helderberg series. 4 Upper Pentamerus limestone. 
Oriskany sandstone. 
Cauda-galli grit. 
Schoharie grit. 
Onondaga limestone. 
| Corniferous limestone. 
[ Marcellus shale. 
Not yet recognized 
in Great Britain. 
Llandeilo fiags. 
Caradoc sandstone: 
Wenlock rocks. 
{ee Sees pectin a) eed Ce 
Hamilton group. 
3 Tully limestone. 
Genesee slate. 
; Portage group. 
| Chemung group. 
Old red sandstone. Old red sandstone. 
Mr. Hall says at p. 24 of his Report, ‘“‘ The geographical divisions 
in this table, though convenient for reference, do not indicate any 
great natural divisions of the system as founded upon fossil characters. 
Such a mode of subdivision will follow only a perfect knowledge of 
the fossils both m this State and elsewhere.’ It thus appears that 
the four great divisions into Champlain, Ontario, Helderberg and 
Erie series have been arbitrarily adopted upon geographical grounds, 
those beds being classed together which are well-exposed in the same 
district. We are therefore at liberty to group the beds together as 
the examination of their organic remains may point out. For as all 
the beds comprised in the New York system are conformably super- 
imposed on one another, there are no natural breaks im the series to 
assist us in subdividing them. 
An English geologist lookmg over the preceding table is imme- 
diately struck by the great number of distinct groups of fossiliferous 
Upper and Lower 
Ludlow and Deyo- 
nian system. 
Erie division. 
. 
| 
