Raymonp.— Correlation of the Ordovician Strata. 
PLATE 4. 
Fig. 1. An exposure of the lower beds of the Ordovician (Walchow and 
Packerort formations) on the Lawa at Wassilkowa. The top of 
the Lower Cambrian is at water-level; the Obolus sandstone, the 
Dictyonema shale, and the Glauconitic sandstone all occur in the 
fifteen feet of strata beneath the projecting beds seen in the middle 
of the figure. The conspicuous beds are the lowest limestone 
and belong to the zone of Megalaspis planilimbata (Bira). Above 
this are seen the softer strata of Brig, then the harder limestone 
of Biz,, and at the top, the zone of Asaphus expansus, or Bris 
(Birra Of Lamansky). 
Fig. 2. Quarry in the upper part of the Walchow and the lower part of the 
Kunda at Putilowa. Both these localities are south of Lake 
Ladoga and east of Petrograd, Russia. 
