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ARTHROPODA 



PHYLÜM VII 



northern parts of Europe, and tliose of tlie middle and soutliern portions. Wliile the 

 niajority of northern genera and si^ecies are common to Great Britain, Scandinavia 

 and Russia, the forms of the central European provinces (Bohemia, Thuringia, Fichtel- 

 berg, the Hartz, Belgium, Brittany, Northern Spain, Portugal, the Pyrenees; the Alps 

 and Sardinia) are so dissimilar as to stand in closer relationships with the North 

 American than with the first-named Trilobite fauna. Of the 350 species found in 

 Norway and Sweden, and of the 275 species in Bohemia, only six are common to 

 hoth provinces, and it is doubtful if these are really identical. 



The first of the accompanying tables shows the ränge and relative development of 

 the Orders and the subclass ; the second represents the vertical ränge of the several 

 families of Trilobites. 



TABLE I 



Diagram Constructed by Beecher showing Relative Development 

 OF THE Orders of Trilobites 



[Table 



