Perner & Kodym — Silurian of Bohemia. 



Art. VII. — On the Zonal Division and Correlation of the 

 Silurian of Bohemia; by J. Perxer, with the collabora- 

 tion of 0. Kodym. 



The Silurian formation in central Bohemia (= Upper 

 Silurian in the sense of European geologists) is repre- 

 sented by three "bandes," designated by Barrande as 

 E 1? E 2 , and F t . The boundaries of these beds were orig- 

 inally not sufficiently defined, and especially that between 

 the most important beds, Ej and E 2 , which was somewhat 

 arbitrary owing to the gradual passage of one into the 

 other ; there has also been a change of opinion as to where 

 and how the boundary line should be drawn between Ej 

 and E 2 . No attempts have been made to divide all these 

 beds, formed chiefly of very fossiliferous shales and lime- 

 stones and attaining at several localities a thickness of at 

 least 500 feet, into minor divisions or zones, as has been 

 very successfully done in other countries. However, Marr 1 

 and Tullberg, 2 in discussing Barrande 's theory of the 

 so-called "colonies," have ascertained the existence of 

 several graptolitic zones in E x similar or analogous to 

 those in England and Sweden. "Wenzel, 3 on the contrary, 

 comparing the Lower Paleozoic deposits of Bohemia with 

 those of Great Britain, endeavored to prove that the 

 geological distribution of graptolites in Bohemia is quite 

 different, and quoted associations of graptolites in E t 

 (on the same slab) which in other countries appear sep- 

 arately in altogether different horizons, and declared that 

 the fauna in the Silurian basin of Bohemia was so con- 

 centrated that no such zones could be distinguished. 



In order to get a reliable basis for a more detailed divi- 

 sion of our Silurian and a closer comparison with that in 

 other countries, I undertook a revision of the Bohemian 

 graptolites, 4 which had been neglected from the paleonto- 

 logical standpoint since 1850. 5 I found in many cases that 

 Barrande had included more than one species under a 

 single specific name, and in some instances had even 



1 Quart. Jour. Geol. Soe., London, 1880. 



2 Sveriges geolog. Undersokning, Ser. C, Xo. 50, 1882; Zeits. deut. geol. 

 Gesell, 1883, 2. 



3 Jahrb. d. geol. Reiehsanstalt, Wien, 41, 1, 1891. 



4 Etudes sur les graptolites de Boheme, I, II, Ilia, b, with 17 plates. 

 Prague, 1891-1899. 



5 J. Barrande, Graptolites de Boheme, with 4 plates, Prague, 1850; 

 E. Suess, Leber bohmische Graptoliten. Haidiger's naturwiss. Abhandl., 

 11, 1851. 



