184 STEATIGRAPHICAL GEOLOGY 



which seem from their graptolites to include representatives of 

 zones from the horizon of the Tarannon shales to the Lower 

 Ludlow (Climacograptus, Mon. priodon, Mon. colonus), succeeded by 

 arenaceous beds (grauwacke) containing Beyrichia Kkedeni and 

 Spirifer elevatus. Above these are sandstones, some of the beds con- 

 taining remains of Placoderm fishes and others Spirifers. 



3. Bohemia 



Passing now to Central Europe we still find in Bohemia a con- 

 centrated and largely calcareous facies of the Silurian with a very 

 rich fauna, the limestone beds being crowded with species of 

 Cephalopods, Trilobites, Corals, Brachiopoda, and Mollusca of 

 various kinds. Some of the species are identical with those of 

 Britain and Western Europe, but many are different, though for 

 the most part belonging to the same genera. The beds which 

 represent the Silurian System are all comprised within the stages 

 E and F of Barrande, the succeeding stages G, H, which he included 

 in the system, having since been relegated to the Devonian (see 

 Fig. 45 and p. 221). 



Barrande divided his stage E into two parts, E x comprising all 

 the shales and E 2 the overlying limestone, but these do not corre- 

 spond with palasontological subdivisions. Moreover, the highest 

 beds of shale are very calcareous and contain large spheroidal 

 limestone - balls or concretions, while layers of shale containing 

 Monograptus colonus are interbedded with the overlying limestones. 



The succession with Barrande's grouping is : 



Feet. 



FI. Black nodular limestone, with graptolites and other fossils . 150 

 E 2 . Grey limestones in thick beds with occasional layers of shale 



(many fossils) ......... 400 



/"Calcareous shales with Mon. colonus and Cyrtograptus Lundgreni] 

 I Black shales with Cyrtograptus Murchisoni .... \%QQ 



1- 1 Shales with Mon. turriculatus ...... j 



^Shales with Rastrites percgrinus ...... J 



750 



The two lower zones are Valentian, the black shales correspond 

 with our Wenlock shale, and the calcareous shale may be equivalent 

 to the Wenlock limestone. The overlying limestones must repre- 

 sent the whole of the Ludlow Series, for they contain a mixture of 

 Wenlock species of corals and brachiopods with such essentially 

 Ludlow forms as Pentamerus Knighti, Dayia, navicula, and Mono- 

 graptus colonus, as well as a host of peculiar trilobites, lamelli- 

 branchs, gasteropods, and cephalopods. 



