SILURIAN ROCKS OF NORTH AMERICA. 
4# 
Fiom the recent researches of M. Paillette it would appear, that beneath certain 
stiata laden with characteristic Devonian mollusca ( Terebratula concentrica, and 
°thei forms allied to that species, with Lepkena Dutertrii, &c.), are slaty schists 
"hich that author identifies with the Silurian schists of Brittany, and containing 
the Calymene Tristani, so distinctive of the Breton slates 1 . 
Whilst such has been the progress in the extension of the palaeozoic classifica- 
tion to different parts of Western Europe, its truth has been conspicuously sus- 
tained by researches in the New World. No sooner were the Silurian rocks distin- 
guished by their fossils and position from all overlying deposits, than several 
geologists of the United States showed, not only that large masses of the Alleghany 
01 Appalachian chain were composed of them, but also that enormous coal-fields 
on its western and northern flanks were deposited on a series of strata very 
analogous to the Silurian rocks of Great Britain. Already geolo gists of several 
of the states have so far published their outlines, that the symmetry of succession 
common to their country and Europe can no longer be doubted. Copious as are 
the subdivisions, to which they have applied numerous local names, we can at once 
recognize in their published fossils, not only the existence of Lower and Upper 
Silurian groups, but also a true Devonian system, the whole forming the base of 
the vast carboniferous deposits of the west 2 . And if any doubt could have been 
1 That some of the Spanish schists are of true Silurian age, is established by their having been found 
M p ^-n™ < ' m ^ SlCrra M ° rena) the Cal V mene Tristani, so characteristic in Brittany. According to 
1 d T ette ’ Certam strata ’ charged with many Devonian mollusks, repose in gentle undulations on beds 
COld and plants °f the carboniferous age (Arnao). If this observation should prove correct, 
1 ^ till more develope phenomena respecting the extent to which land plants descend into the palmo- 
rocks, phenomena to which Professor Sedgwick and Mr. Murchison alluded in their memoir on the 
thenish Provinces (Geol. Trans., vol. vi. p. 262.). 
I he brothers 1 rofessor W . B. and H. D. Rogers, have already published some of their general views, 
V'hieh will be followed by detailed maps and sections, and illustrations of the structure of the Appalachian 
lain in I irginia and Pennsylvania. Mr. Conrad has made us well acquainted with many of the Silurian 
species of Mollusca, and has, by means of the trilobites alone, divided the system into three groups. 
Di. Dale Owen communicated a memoir on the geology of the region of Indiana, with its great coal- 
fields and subjacent palaeozoic rocks, to the British Association and Geological Society of London. 
Dr. Emmons, besides his Report of the northern part of New York, has just published a work, entitled 
ffie Taconic System,’ descriptive of the oldest slaty fossiliferous rocks in Massachussets and the sur- 
rounding states, which is possibly the equivalent of those fucoidal strata which in the countries we are 
a out to describe form the base of the Silurian system?. Dr. Troost of Nashville has described the fos- 
-i ifeious Silurian divisions of Tennessee. To Mr. Vanuxem we are indebted for a volume on one of 
6 ° Ur dlstncts into which the extensive state of New York was divided. Mr. .1. Hall has recently 
P th his detailed researches made during the New York survey, in a clear and copiously illustrated 
If)' 
