202 _ Marcou’s Geological Map. 
species of fossils are restricted to these beds, and more than thirty 
k was so named from its containing great 
numbers of Pentamerus galeatus, this being, with its associated 
shaly limestone, the only position of that fossil. Now our author 
makes the rock Silurian, (p. 25) and describes and figures the 
fossil as Devonian (p. 31). He asserts that it is ‘common to 
Upper Silurian and Devonian of Europe, and is in the same geo- 
logical position in America, but on this side of the Atlantic, it is es 
pecially found in the Devonian division.” Now this fossil is never 
found in any rocks of America included by this or any otber au 
thor under Devonian; nor is it true that it ocenrs in the Devo- 
nian of Europe. Had our author read what was published on 
the other side of the Atlantic as long ago as 1848, he would have 
known this. 
The author cites Upper Silurian rocks as forming ‘the upper 
part of the Falls of the Mississippi at Fort Snelling.” The ex- 
plorations of Dr. Owen and others have shown that the rock 1s 
the Trenton limestone; and it is underlaid by a soft, shaly and 
fucoidal mass representing the Birdseye limestone ; and that this 
rests on a sandstone belonging to the lower formations. It will 
eric 
beds of rock salt.” he italicising is ours, the statement 1st 
author’s. ‘ 
Leaving the Upper Silurian, we find under the Devonian, 4 
ae a assemblage of rocks, as one or two citations will 
10W. ii 
n page 29, our author says, ‘very fossiliferons sandstones 
form the first devonian beds in Pennsylvania and New York} 
then comes a great extent of marl and clay, presenting in certain 
localities quite numerous fossils ; and lastly, the whole is crowne 
by very deep red sandstone, especially at the Catskill mountains, 
. Y., at the base of the Alleghany mountains, Pa., and a 
Gaspé, Lower Canada.” 
* We know something of the rapid growth of western towns, but we cannot sup” 
pose that the environs of Cincinnati extend to forty or fifty miles. sites 
