Raymond.— Correlation of the Ordovician Strata. 



PLATE 2. 



Comparative table of sections of the Lower Ordovician strata in the Govern- 

 ments of Petrograd and Esthonia, Russia. This diagram is redrawn with 

 some alterations from one published by Lamansky. Ai is the Lower Cambrian 

 Esthonia formation, A2 the Obolus sandstone, A3 the Dictyonema shale, 

 Bi the Glauconite sandstone, Bn the Glauconite limestone with its subzones, 

 and Bill the Orthoceras limestone (Kunda formation). The Bus is the 

 Biiia of Lamansky. A2 and A3 make up the Packerort formation and Bi 

 and Bn are the Walchow formation. 



