108 M. Barrande on the Silurian System of Bohemia. 



more important results already obtained by M. Barrande, are 

 chiefly supplementary to Sir R. Murchison's memoir above 

 mentioned. 



Bohemia, as is well known, forms a great basin or moun- 

 tain valley, shut in on every side by walls of ancient granitic 

 and gneiss rocks, except on the north and north-east, where 

 the new red sandstone and more recent formations spread 

 over the older rocks. The longer axis of this basin runs north- 

 east to south-west, from a little south of Prague to Bischof- 

 Teinitz, and is about 20 German (92 English) miles long. 

 The whole interior of this great valley is filled with deposits, 

 belonging to the same period with the Silurian formations of 

 England. These deposits, in general, dip from both sides to- 

 wards the central axis of the valley, and thus form a syn- 

 clinal trough or basin. The dip of the strata is commonly 

 from 30° to 45°, rising occasionally to 70°, or even becoming 

 vertical. 



The whole mass of these rocks occurs in conformable stra- 

 tification, but may be divided from palseontological and petro- 

 graphical characters into eight stages (etages) of which four 

 correspond to the lower, and four to the upper division of the 

 Silurian system of Sir R. Murchison. These are considered 

 by the author in the ascending order. 



The lower division is by far the most extended, both in 

 superficial and vertical dimensions. Resting immediately on 

 the granite are found talcose, chloritic, and other schists, 

 which in some localities, as at Zampach, seem to alternate 

 with it. These schists pass insensibly above, into primary 

 clay-slate {Urthonschiefer), and this as we continue to ascend 

 into schistose conglomerates, composed sometimes of fine 

 quartz grains, at other times of larger masses, more or less 

 rolled, and united by an argillaceous or siliceous basis. These 

 rolled masses, often less than nuts, rarely so large as a man's 

 fist, consist of quartz of various colours, of clay-slate and 

 flinty slate. The whole of these deposits are without organic 

 remains, but from their conformability to the superior beds 

 and gradual passage into them, are considered by the author 

 as the azoic base of the Silurian formation. He divides them 

 into two groups, the lower. A, comprising the crystalline and 



