148 Frof. G. Linjiai^sson — The Oldest Rocks of N. Europe. 



If Mr. Hicks's views of the physical geography of the Cambrian 

 period were correct, there ought to be, in the middle and upper por- 

 tions of the Cambrian series of Sweden, manj'- signs of littoral con- 

 ditions, for Mr. Hicks thinks that the sea first at about the Menevian 

 era reached the Scandinavian area, and much later still the Eussian. 

 The facts, however, rather tend to show that most of the Swedish 

 Cambrian rocks were deposited in a deeper sea and further from the 

 land than the English. The Olenus beds of Sweden consist, as far 

 as hitherto known, invariably of fine schists, containing intercalated 

 bands and nodules of limestone.^ The Paradoxides beds for the 

 most part consist also of similar rocks. Only in their lower portions 

 there occur in some places arenaceous flagstones. If one may judge 

 from the fineness of the sediment, the whole of the Olenus beds and 

 at least the upper portions of the Paradoxides beds— the equivalents 

 of the British Lingula flags and Menevian group — seem, therefore, 

 to have been deposited in a deep sea and far from the land. When 

 we come lower in the series, we find, in Sweden as well as in Britain, 

 many signs of littoral conditions, especially in the Eophyton Sand- 

 stone, where ripple-marks are common, and the lowest part of which 

 is a conglomerate. 



The comparative thickness of the English strata seems also to 

 favour the idea that they weie formed nearer the shore than the 

 Swedish ones. In general more sediment is deposited near a shore 

 than at a greater distance therefrom. 



Finally, the volcanic rocks, which are said to be intercalated in 

 the English Cambrians and Silurians, seem to point in the same 

 direction, as volcanos seem in general to be chiefly confined to 

 littoral regions, whether supramarine or inframarine. In the Swedish 

 Cambrians no rocks which can be considered as volcanic are known. 



The relative ages of the lowest fossiliferous rocks of Russia cannot 

 be ascertained from their fossils alone. These are few in number ; 

 none have been identified with species occurring in other countries, 

 and even the genera — for instance, Schmidtia, JSTelmersenia, and 

 Keyserlingia — are mostly unknown in Scandinavia as well as in Eng- 

 land. I must therefore confess that I have no very decided opinion 

 of their relation to the rocks of other Cambrian districts. Thus 

 much is, however, from stratigraphical evidences, certain, that they 

 are far older than they are supposed to be by Mr. Hicks, who con- 

 siders them to be not older than the Arenig rocks of Britain. The 

 lowest Eussian bed, the age of which can be fully ascertained from 

 palfBontological as well as stratigraphical evidences, is the bituminous 

 schist with Dictyonema flabeUiforme, Eichw. It is of inconsiderable 

 thickness, but forms a well-marked horizon from St. Petersburg 

 along the northern shore of Ehstland to Eeval and Baltischport. 

 Certainly this schist cannot be younger than the Tremadoc period. 

 Its equivalent in Sweden, which has precisely the same lithological 

 and pala3ontological characters, lies immediately above the Olenus 

 Schists ; it is older than the Lower Graptolite Schists, which cor- 



1 Tn Norway they seem to be in some districts partly replaced by sandstones and 

 qnartzites (cf. Brogger, Geol. Foren. Forbandl., Dec. 1875). 



