70 On the Silurian Bocks of Bohemia, and 



want of fossils, seem, liowevei', to me to be so allied by mi- 

 neral characters, and conformity of dip and strike, to those 

 which overlie them, that they must be considered to form as 

 truly the natural bottom of the Silurian basin of Bohemia, 

 as the siliceous sandstones and arkose of Sweden, and the 

 lower shale of St Petersburg (both equally void cf all fossils 

 except fucoids), constitute the base of the Silurian rocks of 

 these countries. 



Amid the numerous species of trilobites contained in the 

 lower schists (c), it is wortliy of remark, that one species 

 (the Faradoxides Tessini) is identical with a foi-m which spe- 

 cially characterises the lowest fossil band in Scandinavia, 

 like which it is also associated with the Battits or A(jnostus. 

 The specimens of the latter genus exceed in consolidation 

 and perfection any thing which the rest of the world has 

 offered, and have been the first to explain the true form of 

 this most curious crustacean, with its rounded head and py- 

 gidium united by two body segments only. Among the few 

 Orthidse discovered in this band of trilobites, is the Or this 

 Bomingeri (Barr.), which is very closely allied to the O. testu- 

 dinaria, so characteristic of the lower Silurian rocks of Bri- 

 tain and other parts of Europe, and which M. De Verneuil 

 has recognised as one of the surest types of the lowest Silu- 

 rian strata of North America. 



These trilobite schists are surmounted by quartzo-schistoze 

 masses (d d" and d^ of the section.) This order is clearly 

 seen near Ginetz on the one side of the basin, and at Skrey 

 on the other, in the gorge of the Beraun, to the west of that 

 village. At the first mentioned places, the rock overlying the 

 schist is a slighly ceyloneritic quartz rock, which passes up- 

 wards into a great mass of siliceous strata, constituting a 

 lofty ridge, usually occupied by forests ; but those relations to 

 the superjacent, as well as to the subjacent strata, are well 

 exposed in the deep narrow valleys of the Beraun and Litawka 

 on either flank of the basin. On the right bank of the Be- 

 raun, near Skrey, the ceylonerite above the trilobite beds is 

 composed of coarse materials, for the most part rounded, 

 of white quartz and black lydian stone, varying in size from 

 that of small pebbles to the dimensions of a man's head. The 



