378 
SILUEIA. 
[Chap. XV. 
large Orthoceras of the group 0. duplex (p. 357), so eminently characteristic of 
this age in the North of Europe. He has, in short, detected about sixty species 
in this zone, a portion of which he has tabulated *. Among these fossils we 
perceive the remarkable Cephalopod with step-like septa, the Bathmoceras, 
Barrande, together with a large Ogygia, Calymene Arago, and Bellerophon 
bilobatus, — the last, which is so typical of these rocks in Britain and France, 
being very abundant. It is also worthy of notice that Agnostus tardus, 
BaiT., which had hitherto been recognized in the upper division only of Stage d, 
makes its first appearance in these much older beds. Here also appears, for 
the first time, Graptolithus priodon (colonus, Barr.), which does not play the 
same part as in Britain by living on through so long a lapse of time (see p. 125) ; 
for, whilst in Wales and Shropshire the latter was in existence from the period 
when the slaty rocks of Snowdon were formed to the time of the Ludlow deposit, 
this same fossil in Bohemia, with all its congeners, reappears no more above the 
Stage e of the Bohemian basin. Again, among the fossils of this zone there are 
Orthidae of three species, a small Euomphalus ? (E. primus, Barr. — belonging 
rather to the many-whorled genus Ophileta of Sutherlandshire and Canada), 
several species of Cystideas and Ophiuridae, with Encrinites, as well as forms of 
the little Entomostracite Beyrichia, which characterizes vast breadths of Upper 
and Lower Silurian rocks in many countries, even in the Arctic Regions. 
Already, therefore, in this very ancient stage, we find many of the types which 
range through the whole Silurian System ! 
The overlying Stages of the great Lower Silurian deposits of Bohemia, or the 
four upper subdivisions of Barrande 's Stage d, correspond on the whole to 
the remainder of the Llandeilo Flags and all the Caradoc formation. But the 
same mineral characters are so persistent throughout the series of numerous 
bands of quartzite, and similar courses of schist are so repeatedly interlaced with 
them from the base to the summit, whilst so many fossils are common to the 
whole, that it has not been found practicable to mark the same distinctions as in 
Britain. Among the fossils which most prevail may be mentioned Beyrichia Bo- 
hemica, Acidaspis Buchii, Placoparia Zippei, Theca elegans, and Ribeiria pholadi- 
formis, — the last having lived on from the earliest-formed strata of this group (d). 
Let me here add a few more words on some striking features of the organic 
remains of this Bohemian basin. Among the Graptolites, G. priodon (Lu- 
densis, Sil. Syst.), which in England is found in all the Silurian rocks, is beau- 
tifully preserved, — its smaller end being incurved. Of Corals there occur quite 
as many Silurian forms as are known in England. The Cystideae of the Lower 
Silurian (Stage d) are occasionally of great size ; and some of them, like the 
Echino-encrinites of Scandinavia and Russia, ascend into the Stage e, or Upper 
Silurian. 
The profusion of Chambered Shells in the basin of Prague has enabled M. Bar- 
rande to trace many gradations between the generic types Gomphoceras, Phrag- 
moceras, Trochoceras, Cyrtoceras, &c. ; and in two specimens of Orthoceras he 
has detected the animal matter in the state of adipocere ! These bodies, 
therefore, he j ustly considers to be the oldest mummies ever exhumed, since they 
occur in Lower Silurian rocks with Trinuclei ! The most ancient Nautilus yet 
found is probably N. tyrannus, Barr., a huge form of a genus of which the author 
has traced some members through all their stages of growth. There are some 
Goniatites, of forms approaching Nautilus ; but no species, not even in the very 
highest strata near Prague, is a known Devonian type. 
* Bull. Soc. Gdol. Fr. sdr. 2. vol. xiii. p. 532. 
