BALTIC REGION 601 



series between the Beekmantownian and Chazyan. The Megalaspis beds 

 of the Baltic region, B II, thus correspond to the early Beekmantown of 

 the Mohawk Valley and the Upper Mississippi, as is also shown by the 

 intimate relation of the Megalaspis beds to the preceding basal Ordovicic 

 Ceratopyge horizon. In the same manner they correspond to the Lower 

 Magnesian series of the Upper Mississippi Valley, which is separated from 

 the Upper Chazyan Stones Eiver beds (Plaitville limestone) by the St. 

 Peter sandstone, shown by Berkey and myself to represent a continental 

 deposit (chiefly eolian) formed during the long interval of exposure. 

 This St. Peter hiatus, as we may designate it, is therefore recognizable 

 on both sides of the Atlantic, and since it is also marked in the Eocky 

 Mountain region (Harding sandstone horizon) and in Nevada (Eureka 

 quartzite horizon), it must be regarded as indicating a universal com- 

 pound eustatic movement, and should be shown in other parts of the 

 world. The evidence for its existence in England and Bohemia will be 

 considered later. 



AVhat the age of the Asaphus beds overlying the hiatus is, is less readily 

 determined. Bassler, on paleontological grounds, correlates it with the 

 Lowville; but he also places the Glauconite limestone in this horizon, 

 which we have just shown to be of early Beekmantown age. 3i The exact 

 equivalency can only be determined from the relationships shown in 

 Scandinavia, though it may be well to call attention again to the appear- 

 ance in this horizon of Ortliis calligraiuma, a characteristic Caradocian 

 brachiopocl. 



CORRELATION OF THE EAST BALTIC AND SCANDINAVIAN HORIZONS 



Returning now to the Swedish occurrences of the Orthoceras limestone, 

 which term, unlike its use in the East Baltic region, where it comprises 

 only the Asaphus horizon, B III, includes in Sweden the Megalaspis beds 

 (B II), we must first turn our attention again to the AVestergotland sec- 

 tions and attempt to correlate the subdivisions there found with those of 

 the East Baltic Provinces. It is evident that the Lower Eed Orthoceras 

 limestone with Megalaspis limbata corresponds to B II a of the Baltic 

 region, while the Lower Chasmops limestone with Ecliinosplicerites au- 

 ra nlium corresponds to C 1 of the Baltic Provinces. This leaves all of 

 the higher Orthoceras limestone to be correlated with the intervening 

 divisions. Incidentally, it may be recalled that the Limbata limestone is 

 separated from the Ceratopyge beds by the Lower Didymograptus shale, 



"'Raymond, who designates the upper beds (B III £ and B III y ) by the name of Kunda 

 formation, makes them equivalent to the Upper Beekmantown of America. In this I 

 strongly disagree with him. They are of late Chazyan, if not of younger, age. 



