Correlation of the Silurian of Bohemia. 63 



nating with shales (Lochkov). The majority of the 

 limestones are finely crystallized. In certain localities, 

 some of the limestone beds consist almost exclusively of 

 the shells of Atrypa linguata, in other horizons this 

 species, is rare. Very common are Pentamerus, Cyrtia, 

 Merista, and Rhynchonella. Graptolites are represented 

 by Monograptus ultimus Per., which, however, continues 

 up to the highest E 2 beds. Records of the occurrence of 

 M. priodon or M. colonics in E 2 are quite erroneous. 



Crinoid Horizon. 



Dark bituminous limestones in thick and thin beds with 

 numerous crinoid remains (chiefly stem fragments, often 

 even loboliths or Camarocrinus), forming locally true 

 crinoid limestones. 16 They are followed by brown or 

 gray, sometimes nodular limestones, alternating with 

 brown shales or shaly limestones, with flat calcareous con- 

 cretions. In this horizon occurs Monograptus ultimus 

 Per., associated with Cardiola interrupta, cephalopods, 

 dendroids (Dictyonema, C alio gr aphis, Besmogr aphis, 

 Rhodonograptus), and Gigantostraca, Some of the 

 limestone beds yield gigantic Orthocerata, as 0. neptuni- 

 cmn, 0. severum, 0. pot ens, 0. pelagicum, 0. temper ans, 

 0. extenuatum, 0. socium, and 0. rivale. In general, the 

 E 2 beds with their frequent alternations of limestones with 

 shales and mudstones, and their changing fauna seem to 

 suggest that they are deposits of a shallow sea-basin, not 

 distant from islands or coral reefs, where the bionomic 

 conditions changed rapidly. 



Distribution of Fossils in E x and E 2 . 



As already mentioned, many fossils have been described 

 by Barrande and others as occurring in E 2 although they 

 are confined to Ej or at least are common to both levels ; 

 this is true chiefly of Mollusca and Crustacea in the lime- 

 stones. These errors have been due not only to the uncer- 



16 These limestones are often very similar to those in E^/ (zone with 

 Monograptus colonus), which also bear in many localities numerous crinoid 

 fragments (stems, loboliths, rarely cups). 



