154 A general Review of the Geology of Russia. 
generalizations on its application to different parts of western 
Europe, and mention that they undertook the exploration of 
Russia in order to test the correctness of these views by obser- 
rocks. ‘These last contain no traces of fossils, and it is prob- 
able 
strata. 
One of the most important results arrived at by the authors in 
their comparisons of the Silurian systems of Sweden and Rus- 
sia, is, that, viewed on a great scale, they are divisible imto two 
periods, each of which has its peculiar palzontological features. 
The inferior period comprehends all from the lowest fossiliferous 
rocks to the argillaceous and calcareous strata of the Island of 
‘othland. ‘The superior epoch, but little developed in Russia, 
(except in the Ural,) embraces particularly the deposits of the 
Island of Gothland and Oesel, which represent the Wenlock and 
Ludlow limestones. 
In the vicinity of St. Petersburg, the Devonian system suc- 
ceeds immediately to the inferior division of the Silurian system, 
and is recognized at first sight by the great number of fishes 
which it affords. These fossil fishes, of which many are identi- 
cal with species found in the old red sandstone of Scotland, are 
found associated with mollusea analogous to those of the calcare- 
ous beds of the Devonian system and those on the banks of the 
Rhine, and confirm the perallelism which the authors of the 
Devonian system have established between these beds.* 
~ *-M. de Verneuil has recently discovered in the Eifel, remains of the Asterolepis 
and Coccosteus and several other genera, associated with the well known shells of 
that country ; one of these specimens sent to rof. Agassiz has been describe by 
him in his monograph of the fishes of the Devonian system, under the name of 
Astedlepien tetiiaghetaits 
