376 
SILUR1A. 
[Chap. XV. 
to their former habitats — a view which, as applied by this great geologist, is as 
original as it is in consonance with natural-history data relating to the migrations 
of marine animals (see p. 380). This Stage (f) is characterized by the first appear- 
ance of true Goniatites, which, as far as I know, have not been observed in so low 
an horizon in any other part of the world. Some of these, indeed, are larger 
than any previously known Goniatites. All intervening bands of shale and 
schist disappearing, the band f is at once surmounted by the highest limestone 
G — a rock usually of small concretionary structure, but which when laid open, 
as in large quarries on the banks of the Moldau (Branik, Wiskocilka, &c), ex- 
hibits extensive flattish masses with slightly undulating surfaces, the upper 
layers of which are covered by grey shale, h of the diagram (p. 371). In these two 
uppermost stages nearly all the other classes of fossils expire j but many Trilo- 
bites still prevail in them. 
M. Barrande refers all these three limestones, including their shales, inferior 
and superior, to the Upper Silurian group, since he has found (as, indeed, I long 
ago anticipated *) that the British division into Wenlock and Ludlow rocks was 
not be looked for in distant lands. In truth, he has detected abundant Ludlow- 
rock fossils in the lower limestone e ; and though the upper Stages, f, g, h, 
contain some of the same species as that rock, they are also distinguished 
by many which are locally peculiar to each of them. In this way Stage F is 
marked by its profusion of Brachiopods ; whilst the Cephalopods, so abundant 
in the lower limestone, are reduced to a few. Of Trilobites, though there are 
seventy-five species, they all belong to the same genera as those of Stage E. 
In G, or the highest limestone, there would seem, at first sight, to be some 
reason for classifying this mass rather as Devonian, seeing that, as well as the 
rock beneath, it contains Goniatites, a genus of Cephalopods unknown in the 
Silurian of Britain, but abundant in the Devonian and Carboniferous rocks of 
many countries. This one feature, however (and the Bohemian species are 
peculiar, and not known Devonian, types), cannot prevail, in the opinion of the 
author, in the face of the much more decisive fact that many true Silurian 
types pervade the three limestones, and unite them in one natural group. Thus 
we here meet with forty species of Trilobites of the genera before mentioned, with 
the addition of Dalmanites (Phacops). Now, although all these genera, with 
the exception of Calymene, are known in the Devonian rocks, no one of the 
Bohemian species has been found in them f j and the resemblance is therefore 
confined to the Brachiopod shells, of which a few species are certainly found in 
Devonian strata J. 
Appended to his work § is an invaluable Table (plate 51, vol. i.), containing 
the result of as much philosophical thought and profound research as were ever 
embodied in a single page of natural-history j and in it M. Barrande brings 
proof at once before the eye, that every one of the few Devonian Trilobites 
belongs to a genus which took its rise and had its maximum development in the 
Silurian period. In other words, they are only the expiring remnants of the 
Crustaceans of the first great natural epoch in which those animals flourished. 
M. Barrande has also defined the upper limit of Silurian life by showing that his 
highest limestone contains three species of Calymene, a genus never yet found 
in the Devonian rocks, the form which was originally taken for a Calymene in 
the lowest Devonian of the Rhine being now recognized as a Phacops. 
* See ' Silurian System,' pp. 196, 301, et passim. I Barrande on the Silurian Brachiopods of Bo- 
t I have the authority of M. Fridolin Sand- hernia, in Haidinger's Naturwissensch. Abhandl. 
berger to state that he knows of none of the 1847, vol. i. 
Upper Silurian Trilobites of Bohemia in the De- § ' Systeme Silurien de la Boheme,' vol. i. 
vonian ro Ls of the Ehine. 
