5'^ JOHAN Kl^R. [SRC. ARCT. EXl^ FRAM 



form, /'sammosteus migrated in Middle Devonian age to the brackish 

 water lai<e,s, — particularly (hose of the south-eastern part of the 

 north Atlantic mainland, and thence to the fresh water lakes. During 

 the Middle Devonian cme form in this manner penetrated into the 

 north of Scotland. In the lower part of the Upper Devonian it extended 

 little hy little along the northern part of the north Atlantic mainland 

 right up to the eastern part of the recent Arctic Archipelago of North 

 America, which presumably formed the north-western border of that vast 

 contineiil. 



The line of this Arctic extension ap|>ears to have 

 played the most significant [)art in the formation of the 

 fish fauna that are described in the present work. 



Printed Marcti 2, 1915. 



