Chap. XV.] 
SILUKIAN BASIN OF BOHEMIA. 
375 
mularium, Rhynchonella navicula, Rh. obovata, Eh. Wilsoni, Rh. marginalis, 
Acroculia haliotis, Pentamerus Knightii, P. galeatus, Spirifer trapezoidalis, 
and forms of Leptaena, all of them published in my original work as Upper- 
Silurian species. Again, most of the Zoophytes which so characterize the 
Wenlock and Gothland limestone are here found in profusion, including the 
widely known Corals Halysites (Oatenipora) catenularius, Favosites Gotlan- 
dicus, &c. Even that fossil which has not otherwise, I believe, been detected 
out of England, the Ischadites Kcenigii, Sil. Syst., has been here collected 
in great quantities. It is also in this rich Stage (e) that the Oephalopods have 
their maximum development, as represented by 400 species in this band only, 
there being among them many species of the true Nautilus. The Crustacea, 
Acephala, Gasteropoda, and Brachiopoda occur in about the same remarkable 
proportion, M. Barrande having described no less than seventy-eight species 
of Trilobites from this one limestone, the chief genera being Acidaspis, Caly- 
mene, Cheirurus, Cyphaspis, Lichas, Phacops, Harpes, Bronteus, Proetus, and 
Arethusina. 
Though M. Barrande has shown that the English fauna of this division has 
many representative and nearly allied forms in Bohemia, the number of fossils 
which are actually identical in the two countries is limited. Thus the 
Phragmoceras ventricosum, P. arcuatum, and Orthoceras nummularium of Bri- 
tain are represented respectively in Bohemia by the Phragmoceras Broderipi, 
Cyrtoceras Murchisoni, and Orthoceras docens of Barrande. In this rich forma- 
tion, Stage e, the Cephalopods alone amount to about 600 species, three- 
fourths of these belonging to Cyrtoceras and Orthoceras ! 
Judging from the fossils, Mr. Salter is of opinion that the subdivision d 
represents the Llandeilo formation ; and other beds and their fossils have been 
compared with the Caradoc. For my own part, however, I have always thought 
that geologists should not endeavour to synchronize any one British subdivision 
with an exact equivalent in distant foreign lands ; and in Bohemia the simple divi- 
sions of lower and upper, as adopted by M. Barrande, are, I think, quite sufficient. 
Ascending from this limestone (e of the section, p. 371), the remaining and su- 
perior stages of calcareous rock (f and g) are so entirely conformable, are so often 
closely knit together in parallel folds in the same hill with the Stage e, and are so 
connected zoologically as well as stratigraphically, that M. Barrande has united 
them all in one natural group, as containing his Third Fauna. The band f, a thin- 
bedded, hard limestone, usually of a light colour and somewhat crystalline, and 
therefore offering a strong contrast to the dark and earthy rock of the beds be- 
neath it, is particularly distinguished from Stage e by a great diminution in 
the number of Cephalopods, which class continues still to diminish in the earlier 
part of the Stage a, but augments again largely in the calcareous zone form- 
ing the upper or later part of the band. It is indeed remarkable that several 
animals which seemed to be extinct, such as Gomphoceras and Phragmoceras, 
reappear in forms very similar to those of the Wenlock formation (e), very 
much lower down. They coexist with Goniatites, fossils wholly unknown in 
any stratum below the Stage f. 
I must refer the reader to the remarkable data brought forward by M. Bar- 
rande (Defense des Colonies, Part iii. pp. 314, 315) which demonstrate that 
there is more specific connexion between the Stages e and f and a Devonian 
fauna than the last bears to his highest Stages g and h. This is one of the 
valid reasons assigned by the author for upholding the truthfulness of the migra- 
tion of certain marine animals in ' Colonies which after an interval returned 
