Dr. H. Trautschold—Periodical Movement of the Ocean. 489 
formations unite with each other from west to east in rows like 
ribbons. The Silurian is in the western part, and its ocean-floor came 
to the surface before the other systems; here was the shallowest part 
of the Silurian sea, and its deepest in the northern half of Russia 
towards the Urals, where the bottom of the Permian sea was laid 
bare last. Here westward from the Urals, even in our days, the 
Rama and Viatka flow to the south into the Volga, which also follows 
this southern inclination. It is evident that the architecture of the 
Paleozoic strata in the northern part of Huropean Russia is as 
follows :—In the west (Esthonia) on azoic foundation, Silurian ; 
towards the south and east with continuation to the north, Devonian, 
with underlying Silurian; east from the Devonian and parallel to 
it, Mountain Limestone, covering Devonian and Silurian; finally 
Permian between Mountain Limestone and the Urals, covering the 
systems just mentioned. When in the northern part of Russia the 
bottom had been left by the Paleozoic sea, the southern part was 
perhaps still covered by a shallow sea with the exception of some 
islands, formed by Silurian, Devonian, and Mountain Limestone 
deposits, as well as by large plutonic masses rising above the water. 
So there were not only deposited the Paleozoic formations, but also 
a part of the lower Mesozoic as Trias, but probably only in thin 
layers, for the most part destroyed afterwards or covered by newer 
deposits. A small remainder of Trias is to be seen in the Caspian 
Steppe (Mount Bogdo) and the Lower Oolite comes to the surface in 
the Crimea and in the Caucasus, From the evidence of this lower 
series of the Mesozoic rocks we may therefore conclude that during 
the Triassic period the ocean receded from the Aralo-Caspian Plain, 
Western Siberia, the Kirghiz Steppes, as well as from the Steppes 
of South Russia, but washing still the crystalline base of the 
Caucasus. The ocean had withdrawn constantly and slowly from 
north to south as far as the basins of the Caspian and Black Sea, 
and this movement had probably begun at the commencement of the 
Silurian period. 
But when this receding movement took place in the northern 
hemisphere, the water must flow off not only to the south, but 
wherever the passage to the ocean was open. So the water that 
had covered the Russian plain had to flow off to the Baltic Sea and 
to the Arctic Ocean. This is in perfect concordance with the occur- 
rence of. Muschelkalk near Berlin, Magdeburg, on the Olenek in 
Siberia, which shows that the deposits with Ceratites were accumu- 
lated at the same time, and that the sea-level during that period was 
almost the same over this area. The higher position of the 
Muschelkalk in middle and southern Germany and in the Alps is 
to be attributed to subsequent movements of the surface of the solid 
crust of the earth. 
It seems, therefore, that towards the end of the Triassic period or 
at the beginning of the Oolitic, European .Russia must have formed 
a similar continent with similar shore-lines as at the present day. 
Only when the sea of that time was inhabited by the Bathonian and 
Kellovian faunas, the renewed rise of the ocean reached again the 
