CHAPTER IV. 
SHIFTING OF FAUNAS. 
EVIDENCE OF SHIFTING OF FAUNAS ASSOCIATED WITH 
DEPOSITION OF ONEONTA SANDSTONE. 
Ill considering the evidence contained in the tables of statistics 
already presented, it is important to note the following points: The 
strata lying above the Oneonta sandstone and below the Catskill, in 
the eastern counties of New York, contain a fauna in which there are 
27 species of the Tropidoleptus carinatus fauna, 5 of which are among 
its most characteristic 12, and 25 of which are reported from genuine 
Ithaca formation strata. The fauna contains 8 species which are 
found in the underlying Ithaca formation, but have not been recorded 
for the Hamilton of this region; 3 of these are in the list of dominant 
species of the Productella speciosa fauna. Finally, there are 25 species 
not recorded from the formations below in the same region, 4 of which 
are among the dominant species of the Spirifer disjunctus fauna, but 
only one of these forms is at all dominant in the eastern fauna under 
investigation. a 
The evidence points clearly to a position intermediate between the 
typical faunas of the Hamilton and Chemung formations. That the 
rocks are younger than the Hamilton formation is shown both by 
stratigraphical evidence and by the occurrence of species that have 
never been discovered in the Hamilton formation. That they are not 
of the same horizon as the Chemung formation containing the pure 
Spirifer disjunctus fauna is shown by the absence of most of the 
dominant species of that fauna, as well as by the strong representa- 
tives of typical species of the Tropidoleptus carina! us fauna; and 
that they are later than the typical Ithaca formation is shown by the 
presence of a few forms not occurring so low as the Ithaca formation 
of the central and western parts of the State. 
The paleontological statistics are thus conclusive in demonstrating 
the intermediate place of the post-Oneonta fauna between the typical 
Productella speciosa fauna of the Ithaca formation, and the Spirifer 
disjunctus fauna of the Chemung; but it does not follow that the 
rocks are intermediate, and therefore not represented in either the 
Portage or Chemung formations farther west. The exact strati- 
graphical equivalency may be shown by a close study of the particular 
local characteristics of the faunules themselves. 
This temporary phase of the general fauna of the zone following 
«See Tables XXV to XXIX. 
Bull. 210—03 7 !>7 
