238 REPORT OF THE AMERICAX COMMITTEE. 
The ohly other point brought forth as decisive is the principle 
of a cycle of deposits according to which the sandstone would be 
regarded as the final stage in the cycle. 
This base of the Devonian, either faunally or lithologically, 
applies only to the eastern area. In the Gaspe section the Oris- 
kany fauna has been reported from the upper part of the lime- 
stone and as high as 1000 feet up in the sandstone. In the 
sections of the central area no evidence has appeared either of the 
faunas or of the peculiar sandstones. Neither in the western 
continental area has evidence appeared of the Oriskany fauna, 
and while the base of the Nevada limestone is distinctly siliceous, 
there is no representative of the Oriskany sandstone of the east. 
That a distinct line of separation between Silurian and Devo- 
nian is to be found in most sections is clear; this is particularly 
the division between Lower Helderberg and Corniferous or lower 
Onondaga limestones; and that Oriskany faunas are transitional 
is equally clear, but on which side of the line they should be 
placed is not as clear. By the Eatonias and allied types the con- 
nection is closer with what goes below; — by the Terebratuloid 
and Spirifer types the Oriskany is closely linked with what fol- 
lows in Devonian. The Fishes and Mej'ostomata Crustacea both 
begin below the Oriskany, and from a faunal point of view M'ould 
lead to placing the division line as low as the Lower Helderberg 
series. However, the common usage in America is that which 
includes the Oriskany in the Silurian, following the precedent set 
by the New York Survey. 
If we look for precedent in the earlier established European 
divisions, we find little help, since the precise details of the faunas 
and rocks are wanting on the eastern side of the Atlantic, as they 
are outside of the Eastern continental area of America. It is more 
than probable that In future classifications the intervals between 
like deposits, as two sandstones or two limestones containing dis- 
tinct though similar faunas, will be found to be a more satisfac- 
tory means of subdivision than the sudden passage from sandstone 
to limestone, from one deposit to another very unlike, although 
they should bear very dissimilar faunas. ^ 
The American treatises on geology, text-books and manuals, 
generally follow the precedent set by the New York Survey of 
including the Oriskany in the Silurian. The United States Geo- 
logical Survey in some of its publications adopts the rule of Oris- 
