THE ORDOVICIAN PERIOD. 339 



the corresponding formations of Bohemia, southern Germany, France, 

 Switzerland, Spain, and Portugal. 



The basis for the separation of the system into two geographic 

 parts is found primarily in the fossils, which are notably unlike in the 

 two provinces, and partly in the nature of the rocks themselves. The 

 north European faunas were more closely allied to those of Asia and 

 North and South America, and were the more general or cosmopolitan; 

 the south European faunas were more local and provincial. 1 An 

 illustration of the wide distribution of certain pelagic faunas is fur- 

 nished by the graptolites. Of 59 species from the Skiddaw slates 

 (Lower Ordovician) of north England, 14 are common to other parts of 

 Britain, 25 to the Quebec group (Lower Ordovician) of Canada, and 

 34 to the Ordovician of Sweden. 2 



The strata of the northern province, except in the British Isles, are 

 essentially horizontal, while those of the southern province are much 

 more generally disturbed. Where much disturbed, they have been 

 notably metamorphosed in both the northern and southern provinces. 



In keeping with the attitude of the strata, the outcrops cover larger 

 areas in the northern province than in the southern. The most ex- 

 tensive outcrop is in the Baltic region of Russia. The Ordovician 

 beds of this region are probably continuous beneath later formations 

 with the Ordovician of the Ural mountains, and the system probably 

 underlies all of northern Russia. 3 Not only does the system no- 

 where appear at the surface over large areas in southern Europe, but 

 there is some indication that the outcropping formations of different 

 regions are not continuous with one another beneath younger beds. 



The formations of the European Ordovician are largely fragmental, 

 being made up of shales, sandstones, graywackes, etc., with which 

 there is associated relatively little limestone. Where the latter occurs, 

 it often has the form of great lenses interbedded with clastic rocks, 

 showing that conditions favorable for its formation were not con- 

 tinuous over great areas. In its paucity of limestone, the Ordovician 

 of Europe is in contrast with that of North America. The constitution 

 of the system as a whole is such as to show that sedimentation was very 

 varied within the area of Europe. The succession of beds is often 



1 Kayser, Geologische Formationskunde, zweite Auflage. 



2 Geikie, op. cit., p. 949. 



3 Geikie, op cit., p. 968. 



