M. Barrande on the Silurian System of Bohemia, 115 



about five German (23 English) miles in length, by one mile 

 (4*6 English) in breadth. It runs from Chodaun, about five 

 English miles south-west of Beraun, to about three miles on 

 the right bank of the Moldau, immediately south of Prague. 

 The whole mass is calcareous with very few intercalated 

 bands of schistose rocks, and is so continuous as to seem to 

 render subdivision unnecessary. The comparison of the 

 fossils, however, indicates four groups or stages, marked 

 E, F, G, H, in ascending order. 



The first stage E is from 150 to 300 metres thick. The 

 basis is well marked by a great formation of trap rocks 

 intercalated in black graptolite schists, with calcareous 

 spheroids like those at the top of the lower division, and 

 containing the same fossils. The traps seem to have been 

 contemporaneous with the shales as they break through the 

 inferior strata, but do not extend into the higher part of the 

 series. The spheroids at first appear isolated among the black 

 shales, but arranged more or less in beds ; they then begin 

 to alternate with thin calcareous layers with the same fossils, 

 and at length approximate, and become changed into continu- 

 ous beds of limestone. This limestone is of a black or dark- 

 grey colour, sometimes compact, at other times crystalline, 

 or in some beds almost entirely composed of remains of en- 

 crinites. It always exhales a disagreeable odour when broke, 

 or is the Stinkstein of the Germans. 



This group has, on the whole, the richest fauna both in 

 genera and species of the entire series. In the Crustaceans, 

 the Trilobites, indeed, fall off three in the number of genera 

 from the preceding group, or 16 to 19, but increase by 25 in 

 species, or 74 in place of 49. To eight old genera eight new 

 ones are associated, completing the development of this tribe 

 in the Silurian seas of Bohemia. No new forms are added 

 in the higher rocks, the size of the species has evidently be- 

 gun to decrease, and this family no longer predominates over 

 the other races. On the other hand, the Cephalopods sud- 

 denly assume an immense development, attaining their maxi- 

 mum, both in the diversity of genera and species, and in the 

 number of individuals. About 220 species are known, dis- 

 tributed in eight genera, as follows : Nautilus, 2 species ; 

 Lituites, 4 to 5 species ; Ascoceras, 7 species ; Thragmoce- 



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