wili.iams.] SHIFTING OF FAUNAS. 115 
of discrimination of the Hamilton formation, the Latter in central 
New York is followed directly by the Tnlly limestone, and that by the 
Genesee shale, in which there is no trace of the Tropidoleptus fauna. 
Farther westward this cutting off of the fauna takes place lower- 
down, and by the time we reach Ohio the Tropidoleptus fauna is 
almost entirely wanting. Still farther on, the highest of this partic- 
ular series of marine faunas is that of the Onondaga. 
In the other direction, when the Genesee shale once comes in it is 
expressive of the departure of the Tropidoleptus fauna from the 
region. Following the Genesee shale eastward we find it gradually 
ceases as a formation, and east of the Chenango Valley very slight 
traces of the sedimentation of the Genesee formation are evident. In 
that region, as soon as the thinning and insignificance of the Genesee 
and Tully become evident in the column, the Tropidoleptus fauna is 
found to extend upward in full strength. In this eastern region there 
is evidence, for several hundred feet of the succession — the direct 
succession — of the Tropidoleptus carinatus fauna, and ils continu- 
ance on until the very base of the Oneonta sandstone. This is evi- 
dence of shifting of the faunas eastward. As the sedimentation of 
the black shale character pushed farther eastward the Tropidoleptus 
fauna was also crowded farther eastward, and in the later part of the life 
of the Tropidoleptus fauna its geographical distribution was restricted 
to this eastern half of New York State, the Cardiola speciosa fauna 
prevailing through the corresponding strata in western New York. 
Now the next clear evidence of shifting of the faunas is found when 
the red shales and sandstones, which are characterized as Oneonta 
sandstones, came in in Otsego County. Coincident with this shov- 
ing in of the shore deposits westward we find the forcing of the 
Tropidoleptus fauna also westward after the zone of the Genesee 
shale was passed. This is represented in the Cayuga Lake section 
b}^ the Ithaca group and its fauna, which is called the Productella 
speciosa fauna. This fauna penetrates somewhat westward of Seneca 
Lake. At High Point the dominant species are of another fauna. I 
have thought that traces of the Productella speciosa fauna appear as 
far west as Hornellsville, but in the section of Genesee Valley no 
trace of the fauna has been discovered. 
The shifting in the other direction, toward the east, is evident at 
the Leiorhynclius globuliforme zone, which follows in the strati- 
graphical succession above the horizon at which the Oneonta sandstones 
cease in the Chenango Valley. Here is indicated a shifting back- 
ward of the faunas which were so dominant in the region of the 
Cayuga Lake section about Ithaca and for 50 miles eastward. The 
shifting is indicated by the withdrawal of the red sediments, also. 
farther eastward, and in the Ithaca section if is indicated by the 
cessation there of the Productella speciosa fauna, followed by a return 
of the species of the Cardiola speciosa fauna of the Portage formation 
