234 REPORT OF THE AMERICAN COMMITTEE. 
ish sandstones and arenaceous shales, with some plant remains 
and a sparse fragmentary fauna which closely resembles in general 
character the fauna of the similar upper Devonian black shales 
of the eastern continental area. 
In these western sections there is a remarkable difference in 
the range and habit of species. " Sorne species," as Mr. C. D. 
Walcott has shown, " have reversed their relative position in the 
group as they have been known heretofore, and others have a 
greater vertical range " (Pal. of the Eureka District, p. 4). Some 
cases mentioned by Mr. Walcott are Orthis Tulliensis at the top, 
Orthis impressa at the base, and several Corniferous corals at the 
upper horizon (see pp. 4 and 5, etc.). 
It is also noticed that the faunas in the higher shales show 
combinations of Devonian and Carboniferous types (White Pine 
Sliales), but a careful study of the species reveals the characteristic 
changes of the general fauna that are seen in the eastern sections. 
For instance, the new type of Brachiopods belonging to the 
genus Produelus (called ProducMla in the New York Reports) 
begins in this western section with certain small forms typical of 
the lower and middle Devonian of tlie east, and it is only in the 
upper horizon that the larger Chemung types of Prod actus appear. 
The same thing is seen in the changes in the types of Spirifera. 
The characteristic upper Devonian /Sp. disjuneta appears only in 
the upper part of the section as in the east. The peculiarities of 
this western section in its paleontology, are most readily explained 
by the assumption, supported also by other facts, that throughout 
the whole age the deposits of this area were made in a wide, open 
ocean, with islands, perhaps, but with no great masses of land to 
disturb the general uniformity of the conditions of life. 
The central area was, doubtless, at considerable distance from 
land but in no great depth of depression. The eastern conti- 
nental area from Michigan around through Canada, New York 
and down the Appalachians, must have been during the Devo- 
nian age, near enough to shores for the faunas, as well as the 
nature of the deposits, to be affected by the ocean currents, and 
to feel strongly the effects of relatively small amounts of change 
of level between land and water. Here the faunas are both more 
local and more limited in geologic range, changing more sud- 
denly and fully in their combinations and species. The condi- 
tions of the eastern border were those of rough and tempestuous 
coasts. 
