230 
IOWA ACADEMY OP SCIENCES. 
same questions that have so long perplexed investigators in 
this country, are momentous problems yet not fully solved 
in Russia. Yet, a comparison between the two widely sep- 
arated provinces throws some light on our own perplexities. 
The basins occupied by the upper Paleozoic in Russia, and 
the Mississippi valley, are very nearly of the same size. In 
the first mentioned area the Permian very greatly predomi- 
nates as the surface rock; in the last named, the coal measures. 
The Carboniferous of Russia presents two very distinct 
aspects: a thalassic facies, occurring on the western flanks 
of the Urals, and made up of limestone chiefly; and a 
shallow water or littoral phase, that is coal-bearing, which is 
best developed in the southern and western parts of the great 
area, principally in the Donetz and Toula basins. 
COMPARISON OP GENERAL SECTIONS. 
RUSSIA. 
CHARACTER OF TERRANES. 
MISSISSIPPI VALLEY. 
Tartaran, Permo- Trias: 
or Upper Permian, P3. 
Shales and marls, red and varie- 
g-ated, sandstones, shaly, fos- 
sils rare, “red beds.” 
Cimarron series. 
Middle Permian, P 2 . 
Lower Permian, Pib. 
Upper Permo-Carbonifer- 
ous (base of equal P), 
CPc. 
Limestones, some dolomitic,and 
calcareous marl. 
Sbale,only 200 feet thick in Kama 
valley. 
Limestone, heavy, doJomitic. 
Marion li. 1 
y Series. 
Chase li. J 
Artinsk, CP. 
Shales, sandstones, some thin 
limestones. 
( Neosho. 
< Cottonwood. 
( Wabaunsee. 
Upper Carboniferous, C3. 
Limestones and shales, hig-hly 
fossiliferous. 
Missourian series. 
Moscouan, Middle Car- 
boniferous, C 2 . 
Shales, sandstones, thin lime- 
stones, coal-bearing-. 
Des Moines series. 
Lower Carboniferous, Ci. 
Limestones chiefly, some shale 
and sandstone. 
Mississippi an. 
In the consideration of a theme like the present one it is 
recognized at the outset that comparisons of terranes of dif- 
ferent geological provinces involve no necessary exact syn- 
chrony, except through absolute physical means of correlation. 
Such a standard, independent of intrinsic features of the ter- 
ranes is not yet formulated for widely separated districts. The 
shortcomings of the common fossil criteria, in any other than 
the most general way and in the absence of something better, 
are well known. Any agreement of biotic features in strati- 
graphic successions distantly removed from one another are 
