Standard for American Carbonifcrons. — Kcycs 305 
and wholly different in origin from it. On the other hand, 
in the west the marine deposits, which must be its equivalent, 
merge above with the later Carboniferous formations of like 
origin and lithological character. With no shore representa- 
tives in the west between the marine Mississippian and the 
marine Missourian formations, and the rock sequence being 
unbroken, the marine facies of the Arkansan and Des Moines 
are important features for determination. 
While westward the littoral formations known in the Mis- 
sissippi valley as the Arkansan and Des ]\Ioines series have 
no representatives of like origin, their eastward extension is 
not so difficult to follow. The Arkansan, so enormously thick 
in the typical locality, thins out rapidly eastward. Although 
its exact equivalents have not been carefully followed through 
Kentucky, Indiana and Ohio to Pennsylvania, it seems that it 
m(ay be regarded asi probably representing very nearly the 
interval occupied by the Pottsville in the last mentioned state. 
This interpretation has additional weight on account of the 
fact that all present evidence goes to indicate that the Alle- 
ghany series of Pennsylvania and the Des Moines series of 
the Mississippi valley are about equivalent stratigraphically. 
The late floral detemiinations of White* also go to support 
this statement. 
Of the Pennsylvania section the interpretation advanced 
would make the Conemaugh and the Monongahela, and prob- 
ably also the Dunkard (so-called Permian) littoral and coast- 
al representatives of the Missourian ; for it is not now believed 
that any part of the so-called Permian in Pennsylvania is so 
high stratigraphically as the base of the so-called Permian of 
Kansas. 
It is not thought that the Oklahoman has any depos- 
itional equivalents in the east. Until recently it was believed 
that the Cimarron or Red Beds of Kansas would eventually 
prove to belong to the Triassic or Cretaceous, but late inform- 
ation seems to show that the formation doubtless is a part of 
the Carboniferous. 
*U. S. Geol. Siir., Mon. xxxvii, 1899. 
