Raymonp.— 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. A: is the Lower Cambrian 
Esthonia formation, A: the Obolus sandstone, A; the Dictyonema shale, 
B,; the Glauconite sandstone, By; the Glauconite limestone with its subzones, 
and Biz the Orthoceras limestone (Kunda formation). The Bis is the 
Birra of Lamansky. A» and A; make up the Packerort formation and B, 
and By; are the Walchow formation. 
