Review of Recent Geological Literature. L2I 
Freeh, Tschernyschew, and several others, have, by contributions direct 
or indirect, endorsed and fortified these determinal inns, until to-day the 
post-Silurian age of these and equivalent 1'aunas. including the Lower 
Helderberg of New York, is no longer debatable. All of these so-called 
"Hercynian" faunas, so far as they had been previously studied, were 
originally determined as Upper Silurian. Barrande's conception of the 
age of his upper etages applied to them all: admitting the correlation 
of the normal Upper Silurian with his etage E, he regarded the super- 
jacent etages P\ <J, II, as a continuation of the Silurian not represented 
in the typical sections of (ireat Britain, thus a y/W-ly pical-Silurian. 
The inclusion of all such faunas within the limits of the Devonian is 
simply the placing within the latter time-division a series of faunas 
more or less highly impregnated with derival ivesof the normal Silurian. 
This Silurian element is evident in the Hart/, faunas, decidedly more 
conspicuous in the Bohemian etages and emphatically less pronounced 
in the Lower Helderberg fauna. In the correlation of newly discovered 
faunas with these Hercynian faunas, there may he a predominating 
agreement with the major Devonian or the minor Silurian element. 
Thus, in Tschernyschew's list of 140 species from this east-Ural Hercy- 
nian, subtracting first 53 new. and '.) undetermined species, there are 35 
out of the 61 remaining which are regarded as identical with species 
occurring in the Bohemian etages Fand <», and of these 35 there are 13 
which also occur in the etage E, or normal Silurian. This:..") is certainly 
a large commotity between so distant faunas, but the large third of 
these, which embodies the specific continuations from the Silurian, in- 
dicates what is perfectly (dear from a consideration of the other two- 
thirds of the Bohemian element, that this tract ion dues not represent 
the Devonian element of the Bohemian faunas, but rather its more dis- 
tinctly Silurian or neutral elements. 
Comparison of the fauna with that described by the same author as 
Hercynian on the west slope of the Urals, shows a contingenl of -'s com- 
mon species, and this element is. as a whole, more Devonian in aspect, 
than the Bohemian contingent. This fact, together with the Devonian 
affinities which are otherwise indicated in the fauna itself, shows that 
the east-Ural fauna, if properly regardedasa single fauna! assemblage, 
is as weak in Devonian types and as strong in Silurian types as ,-i I Devon- 
ian fauna can well be: that is. it indicates, if Devonian age, a Devonian 
stage that has heretofore been unrecognized. 
While the conventions of geology, the lapses in our knowledge of the 
geological record and the finitllde of human comprehension render nec- 
essary t be employment of such lime divisions as Silurian. Devonian, 
etc. (and we are disposed in believe that some few years will have 
elapsed before such terms can be dispensed with, notwithstanding the 
evideni impatience of them manifested bj some of our twentieth cen- 
t ury geologists), our conception of the limitation of such lime divisions 
and their faunas musl be materially influenced b\ the limitation of 
their original definition. As a series of rocks the upper limn of the typ- 
ical Silurian section was clearh defined, and time has shown that ibis 
