Trof. G» Linnarsson — The Oldest Bocks ofK. Europe. 149 



respond to the Arenig and Skiddaw rocks of Britain, and is severed 

 from them by the Ceratopyge Limestone, which might be com- 

 pared to the Upper Tremadoc of Britain. Below the Dictyonema 

 Schist there are at St. Petersburg and in Ehstland mighty beds of 

 sandstone and shale, several hundred feet in thickness. That they 

 are older than the Tremadoc period is shown by their position. 

 Any further conclusions relating to their age cannot be based on suf- 

 ficient evidences. Their uppermost part seems to be nearly related 

 to the Dictyonema Schist ; the age of the lower parts remains still 

 to be definitely settled, which will not be possible before more is 

 known of their organic remains. Lithologically, they very mnch 

 resemble the Fucoid and Eophyton Sandstones of Sweden, though 

 they are more friable. I have, therefore, suggested that they 

 might have stood in immediate connexion with those Swedish 

 beds.^ In favour of such a supposition speaks, besides their litho- 

 logical characters, their position immediately above the crystalline 

 rocks. In an opposite direction points, on the contrary, their relation 

 to the overlying rocks, as they are immediately, and seemingly with- 

 out any sharp break, overlain by a rock, the Dictyonema Schist, 

 of much younger age than the Paradoxides Schists overlying the 

 Fucoid Sandstone of Sweden. However this may be, it is probable 

 that Mr. Hicks is right in thinking that the Cambrian rocks of 

 Russia, at least in part, are deposited in a more shallow water than 

 those of Scandinavia. 



Of the Cambrian rocks of Bohemia Mr. Hicks says that '' they 

 seem to occupy an almost intermediate position, as to thickness and 

 order of deposition, between those of Britain and those of the ex- 

 treme north." This might possibly be true as to the so-called 

 " Azoic" rocks of Mr. Barrande, respecting the age of which no posi- 

 tive conclusions can be drawn from fossil evidences. That they are 

 in part older than any metamorphic rocks of Scandinavia is not im- 

 possible; and if the lower portion of the stage B, the "Przibramer 

 Schiefer " of Austrian geologists, really lies unconformably under the 

 upper portion of that stage and conformably over the crystalline 

 schists, it is, indeed, rather probable. The '' Primordial zone," or 

 stage C, of Bohemia is, however, much younger than the oldest fossil- 

 bearing strata of Scandinavia. It is most nearly related to some of the 

 middle divisions of the Swedish Paradoxides Schists, especially to 

 those with Paradoxides Tessini and those with Paradoxides oleadicus. 

 That any absolutely identical species occur is not yet quite certain ; 

 but of the Primordial Trilobites of Bohemia, many are represented 

 in the Swedish beds by very nearly allied species. Such are, for 

 instance, Paradoxides Tessini and spinosus, Ellijpsocejplialus Hoffi and 

 Agnostus rex. 



It seems still to be premature to speculate on the way followed 

 by the Cambrian faunas in their migrations. In order to do that 

 with any certainty it would be necessary to know in every instance 

 whether the rocks containing the same faunas are really synchronous 

 or only " homotaxial." At present, it seems quite as probable that 

 ^ Zeitschrift der Deutschen geologische Gesellschaft, Jahrg. 1873, p. 691. 



