wim.iams.] SHIFTING OF FAUNAS. 109 
vivid illustration of the fact. As a formation the Oneonta is a well- 
defined body of rock in Otsego County, New York, occupying a defi- 
nite place in the geological column of the Devonian. 
The evidence we have been examining, however, leads to the belief 
that the particular part of the geological column which was being 
formed in eastern Ohio at the time of the deposition of the Oneonta 
formation in eastern New York is not a sandstone but a soft sand 
shale called the Ohio shale. If we follow these Ohio shales eastward 
we find that they become coarser, and when we reach the Genesee 
Valley the sediments are still fine shales with some sandstones, laid 
down in even-bedded, sometimes flaggy, layers, with. few fossils, and 
the fossils belong to a fauna quite different from that of either the 
Hamilton below or the Chemung above. The rocks here are known as 
the Portage formation. Following the rocks occupying the same geo- 
logical horizon still eastward, by the time we reach the meridian of 
Cayuga Lake and Ithaca the same part of the column is represented 
by argillaceous and sandy shales alternating for several hundred feet. 
Many of the layers are rich in fossils and contain species of both the 
lower Hamilton and the higher Chemung formations, together with 
certain peculiar and characteristic species which have come in from 
elsewhere or have been evolved from the faunas prevailing at the 
lower horizons. In the midst of these sediments there are beds of 
flagstones and, locally, of massive sandstones. In this region the 
rocks are known as the Ithaca group or formation. Following the 
sections still eastward as far as Chenango Valley, the flagstone quar- 
ries of Norwich, Oxford, and Greene townships are found occupying 
the place of the more fossiliferous Ithaca zones farther west. 
Still farther east, the Oneonta sandstones, including red sandstones 
and even conglomerates, with fish remains and some plants, but hold- 
ing very slight traces of any marine fauna, occur in considerable 
thickness. From the evidence at present in sight I conclude that this 
series of sandstones is continued eastward without interruption and 
is probably a portion only of what is called the Catskill formation of 
the Catskill mountain region. Theoretically this is assumed to be 
the fact. 
If now we analyze the distribution of these sediments, which are 
supposed to have been laid down during the same epoch of time, we 
find that four distinguishable classes of sediments may be recognized 
as in process of deposit at different areas of the bottom at the same 
time. These may be spoken of as (a) the black shale, (b) the rela- 
tively barren Portage shale, (c) the fossiliferous argillaceous shales, 
and (d) the red sandstones. 
BLACK SHALE SEDIMENTS. 
The Ohio shales are a continuation upward of what is called the 
black Genesee shale in other regions, and consist of a series of fine- 
grained somewhat arenaceous sediments which have the peculiarity 
