374 
SILUKIA. 
[Chap. XV. 
In a letter to myselt in, 1863, M. Barrande made the following important 
observations : — 
" This fauna (from the environs of Hof ) presents evidently ' Primordial ' characters, 
by the predominance and the forms of its Trilobites, which are accompanied by a 
small number only of the usual Lower Silurian genera, i. e. Lingula and Discina, the 
Pteropod Pugiunculus, and a Cystidean. 
" The Trilobites predominate, indeed, over the other fossils, both in the number of spe- 
cies and in the relative quantity of individuals : I recognized eight to ten species of Cono- 
cephalus and Olenus, all new, as well as another type which also seemed to me to be new. 
With these ' Primordial ' Trilobites are also associated two or three forms which every- 
where characterize the Second Silurian fauna (Llandeilo and Caradoc), i. e. Calymene 
and Cheirurus. 
" The coexistence of these different types is evident, since I found them in the same 
piece of rock not larger than my hand. 
" The occurrence of the genus Olenus, which is entirely absent in Bohemia, and the 
appearances which the species of it present, indicate that the fauna of the environs of 
Hof has more relation to the English and northern zone than to the central zone of 
Europe. There was therefore (of old) a gneissic barrier, more or less elevated, be- 
tween Bohemia and Bavaria, such as that which we now see. 
" I was drawing up an interesting parallel between these two Palaeozoic basins ; but 
just as I was about to complete it, I was obliged to quit Prague ; and since then I have 
been absorbed in very different occupations. 
" You will observe that the partial coexistence of the Primordial and Second faunas , 
on the frontier of Bohemia comes in very a propos to aid us in the conception of the 
partial coexistence of the Second and Third Faunas in Bohemia, or, in other words, of 
my ' Colonies.' " — Quart. J ourn. Geol. Soc. vol. xix. p. 362. 
But, to return to a description of the Silurian basin of Bohemia. The next zone, 
or 1 Stage d,' of the typical basin of Barrande, is formed of schists and sand- 
stones, and represents the great upper mass of the Lower Silurian, charged 
with abundant casts of Trinucleus, Ogygia, Asaphus, Illsenus, Remopleurides, 
and many other Trilobites. In it also has been observed the same relative 
development of the genus Orthis among the Brachiopods, and of Cystideae 
among the Echinoderms, which stamps the character of the Lower Silurian 
rocks of Scandinavia, Russia, Britain, and North America. 
Prague, with its Imperial palace, the Hradschin, stands upon these Lower 
Silurian rocks, which, dipping under Upper Silurian schists and limestones 
to the south of the city, rise up again to the surface on the banks of the Moldau, 
a few miles further south, and thus exhibit the upper members enclosed within 
a trough. 
M. Barrande places the base of his Upper Silurian, or bottom of his * Stage e,' 
where the quartzites with Trinuclei are overlain by black schists with large 
concretions or ballstones, and containing many Graptolites. Several bands of 
greenstone, which the author considers to be of cotemporaneous age, are inter- 
polated in this portion of the series j and the shales are followed by grey argil- 
laceous limestone replete with a very rich fauna, unquestionably of an Upper- 
Silurian type. Although it might be contended, however, that, as in other coun- 
tries, the schists which contain both the doubly and singly serrated Graptolites 
ought rather to be classed with the lower division, no one can doubt that the 
limestones into which those schists graduate upwards represent the true Upper- 
Silurian type, so well marked in England and Gothland. Thus, in these we 
meet with the well-known fossils Cardiola interrupta, C. fibrosa, Phragmoceras 
ventricosum, P. arcuatum (Cyrtoceras, Barr.), Orthoceras annulatum, O. num- 
