SILURIAN 8YSTKM 183 



are also beds of oolite and of marly limestone which arc ridi in 

 Spongiostroma, a kind of calcareous alga, and thin bands made up 

 of Sphcerocodium, which is another alga of solid globular form. 



The succession of beds found in these three districts is given in 

 an abstract form on p. 182, the figures 1, 2, 3 indicating the equi- 

 valents of the Valentian, Salopian, and Downtonian Series. 



From the above account it will be seen that the Silurian of 

 Qottland is quite an abnormal development of the system, and as 

 such is not at all suitable to be taken as its typical fades. Hence 

 the fashion which has come into vogue among continental geologists 

 of using the term Gothlandian instead of Silurian is unfortunate 

 and unnecessary. 



It will be noticed that the equivalents of our Uandovery and 

 Wenlock Beds are of comparatively small thickness, and that 

 throughout the Scandinavian region the larger part of the sediments 

 belong to the time of our Ludlow Beds with representatives of the 

 Downtonian in Scania. 



The highest beds are most fossiliferous in the Ramsasa district 

 of Scania, where they are often full of Leperditia incequalis and 

 Tentaculites. Homalonotus Knighti, Phacops Downingiv, Spirifera 

 elevata, Pterincea retroflexa, and a Pterygotus also occur. 



2. Russia 



The Gottland type of the system is found again on the Russian 

 side of the Baltic in Esthonia and Livonia, the beds having clearly 

 been once continuous across the intervening space. From the 

 following table it will be seen that they are very little thicker 

 than in Qottland, when allowance is made for their forming a 

 more complete succession both at top and base. 24 



FMt. 



/ Grey and yellow limestones with Eurypterus Fischeri, Hemwspis 

 \ rugosa, Platyschisma helicites ..... 60 



Dolomite and marls, with a Wenlock fauna 



2- Limestone with Pentatnenis estonus and Jllcenus barriensis 

 I passing into a coralliferous limestone 



{Raikull Beds with few fossils (Phacops elegans) . 

 Limestone largely composed of Pentamerut borealit 

 Joerden Beds shales and marls with Encrinus punctatus 

 IHiiiachonella affinis, and corals 



60 



50 

 100 

 30 



25 



::'.!& 



These beds pass southward beneath the Devonian Series, and 

 when the Silurian reappears in Russian Poland near Eielce it 

 presents a very different fades. The sequence has not yet been 

 completely worked out, but consists in the lower part of shales 



