BRACHIOPODA. 



229 



w 



H 

 W 

 B 



B 

 t-' 

 f 

 > 



O 



V 



K 



en 



I I 



I I 



Lower Cambrian. 



Mkidle Cambrian. 



Upper Cambrian. 



Calciierous. 



Cliazj^ 



Trenton. 



Utioa. 



Hudson Kiver. 



Clinton. 



Niagara. 



Lower Ilelderberg. 



Orislvany. 



Upiu'r lIGlr^crbor^^ 



Hamilton. 



Cliemung. 



Waverly. 



Burlington. 



Keokuk. 



St. X^ouis. 



Kaskaskia, 

 Chester. 



L,r. Coal Measure. 



Middle and Upper 

 Coal Measure.'*. 



Permian, 

 Triassic. 



