1847.| SHARPE ON THE PALZOZOIC ROCKS OF N. AMERICA. 149 
beds recognized as existing below the old red sandstone ; but he will 
be much mistaken if he supposes these to have any analogy to the 
great groups of beds to which we have attached distinguishing names 
in this country. The difference lies in the greater degree of subdi- 
vision adopted by the New York geologists, who have given a separate 
name to every bed which offers any difference, either of mineral 
character or of fossil contents, from the beds adjoining it, whether its 
thickness be 10 or 1000 feet ; so that if we were to name on the same 
principle all distinguishable beds between the old red sandstone and 
the bottom of the fossiliferous rocks of Wales, we should probably 
have to give them above a hundred different names. 
Such subdivisions may be convenient for local purposes, but they 
ought also to be thrown together into a second series of larger groups 
representing the more important divisions. The want of such en- 
larged classification has led to very erroneous conclusions in the 
comparison of American and European formations: thus all the Ame- 
rican geologists have adopted the opinion set out in Mr. Hall’s table, 
that fossiliferous beds are found ia New York of a much earlier period 
than any beds known in Europe: for having ascertamed that the 
division between the Niagara and the Clinton groups corresponds to 
that between the Lower Silurian and the Wenlock formations in 
England ; and finding eleven groups of beds below this line in the 
United States, while we in England have only distinguished two or 
three, they have come to the conclusion that they have many groups 
containing organic remains older than any of ours. A slight resem- 
blance in mineral character between the Utica slate and the Llandeilo 
flags, has been caught at to strengthen this opinion. 
Instead of admitting this view of the greater age of the lowest fos- 
siliferous beds of the United States, I can see no grounds for be- 
hieving that any such beds have been there discovered of an earlier age 
than the lowest fossiliferous beds of North Wales, by which I mean 
the beds in the neighbourhood of Tremadoc contaming Lingule, 
discovered by Mr. J. E. Davis (Journal of Geol. Soc. vol. i. p. 70), 
the position of which has since been better determined by Professor 
Sedgwick (Journal of Geol. Soc. vol. i. p. 140, &c.). It is true 
that I have not been able to recognize as Kuropean any species found 
in beds below the Trenton limestone ; but in that bed and its equiva- 
lent in the west, the blue limestone of Ohio, we find many of the 
Species which are common here in the upper and middle parts of the 
Lower Silurian formation, but none of those peculiar to the base of 
that system. Mr. Hall mentions with some doubt the Il/enus cras- 
sicauda as occurring in the Chazy limestone ; this trilobite is found 
here in the limestone of Rhiwlas near Bala: even if the synchronism 
of these two beds were admitted upon this slight evidence, it could 
only follow that the lowest fossiliferous bed in the United States, the 
Potsdam sandstone containing Lingulee and fucoids, was about of the 
same age as the Tremadoc bed containing Lingulze and some bivalves; 
but this would not show a greater age in the American bed. As I 
must return to this subject again, I will not follow it farther at 
present. 
