66 Perner & Kodym — Zonal Division and 



Diversa: Scyphocrinus decor atus W. & J.(l)', 8. excavatus 

 (Schl.)(l), 8. subornatus(l), Bohemicocrinus pulv evens (1-2), 

 Aulopora disjecta Poc.(l), Desmograptus plexus Poc. (1-2?), D. 

 giganteus Jahn(l), Dictyonema bohemicum (1-2), D. confertum 

 Poc. (1-2?), D. grande (1-2?), D. graptolithorum Poc. (1), Inocau- 

 lis attrita Poc. (1). 



Bande F 



The highest member of the Silurian series in Bohemia 

 is the dark limestones which have been referred by Bar- 

 rande to his Etage F and designated as F^ Their litho- 

 logic and faunistic characters place them much nearer to 

 the E 2 beds than to the F 2 limestones, which are undoubt- 

 edly of Lower Devonian age. 19 In addition, a faunistic 

 hiatus between F x and F 2 , signifying the boundary line 

 between the Silurian and Devonian in Bohemia, together 

 with the decidedly Silurian aspect of the Fj fauna, points 

 out the closer connection of Fj with E 2 . 



The boundary line between E 2 and F x is marked by the 

 occurrence of hornstones in the limestone, and by a 

 change of fauna. As in E x and E 2 , there are two facies 

 developed in F x . The reef facies, which in F 1 has a far 

 greater extension, is formed of limestones with very sub- 

 ordinate shales. The limestones in the lower part of F x 

 are dark, nearly black, fine-grained or compact, thickly 

 bedded, and contain dark hornstones of irregular shape ; 

 shaly reddish intercalations occur only in the lowest beds. 

 In the upper part the limestones are lighter, gray or 

 whitish, thinly bedded, finely or coarsely grained, resem- 

 bling the white limestones of F 2 , but contain yellowish or 

 reddish hornstones. Opposite Tetin this facies is fossil- 

 iferous, bearing almost the same coral fauna as in E 2 . 



The other, "normal" facies is more shaly, and is lim- 

 ited chiefly to a seam between Prague and Kosor (valley 

 of Radotin). Characteristic are dark fine-grained lime- 

 stones, splitting into flat plates and alternating many 

 times with dark or brown shales ; hornstones are rare or 

 completely missing. 



As for the fauna, it is quite different from the contem- 

 poraneous coral fauna, and differs also from the "nor- 



19 It would perhaps be more appropriate to call the Fi beds E 3 , so that the 

 Silurian of Bohemia would correspond to Barrande 's Etage E, and the letters 

 F, G and H could be reserved for the Devonian. Some Bohemian geologists 

 have already accepted this proposition. 



