DEVONIAN SYSTEM : WETWIN SHALES. 



245 



Afetwin Fauna. 



DEVONIAN OF 

 AMERICA. 



Europe. 



Remarks. 



Lower. 



Mid- 

 dle. 



| Upper. 



Helderberg Gr. 



Corniferous Gr. 



Hamilton Gr. 



Portage Gr. 



Chemung Gr. 













Carb., Ireland. 



. — 





X 























Carb., Ireland. 















Mid. Dev., Devonshire. 





• • 



X 

















X 



X 







• 













Dev., Germany. 









X 















X 







Mid. and I 'p. Dev., Britain. 





