68 CORRELATION OF GEOLOGICAL FAUNAS. [bull. 210. 
ABSENCE OF TROPIDOLEPTUS FAUNA IN OTHER REGIONS. 
That the Tropidoleptus fauna is not represented in the Iowa forma- 
tions is signified by the fact that only Phacops rana of the standard 
list — a species of very wide geographical range — appears in the lists 
consulted. 
The Manitoba, Saskatchewan, and Mackenzie River lists prepared 
by Dr. Whiteaves do not record a single species of the standard Tropi- 
doleptus carinatus faunal list. 
We are thus led to the separation of the Devonian faunas of Iowa 
and the Northwest (outside the intercontinental basin) from those of 
the Appalachian province and its extensions, both into the Tennessee 
province and into the Michigan province, with the latter of which, 
faunally, the Milwaukee localit}^ must be regarded as directly con- 
nected. 
POST- HAMILTON FORMATIONS AND THEIR FAUNAS IN NEW 
YORK PROVINCE. 
Having demonstrated the dominant characteristics of the fauna 
which is contained in the Hamilton formation in its central position 
and where the facts are most fully known, we have next to consider 
the faunal characteristics of the overlying formations. The upper 
termination of the Hamilton was, for the purposes of this investigation, 
assumed to be at the bottom of the Tully limestone, where that is 
present; at the bottom of the black Genesee shale, where that is clear 
and the Tully is not evident; and, where the evidence of those ordi- 
narily overlying formations is indistinct, at the place in the sequence 
of strata which can be definitely traced, by either stratigraphical or 
paleontological evidence, as the stratigraphical extension of that plane. 
It is also taken for granted that the list of species given in Table V 
may be relied upon as positive evidence of the Tropidoleptus carinatus 
fauna as it is expressed in the northeastern corner of the continental, 
basin of North America. The entire absence from any fossil faunule 
of the 12 species there enumerated may be regarded as presumptive 
evidence that the Tropidoleptus fauna is absent, although other species 
among the 200 or more thereof known to be and found associated with 
them might be present. 
On the other hand, the presence of the majority of these dominant 
species is not proof positive that we are dealing with the stratigraphical 
equivalent of the Hamilton formation, for the two following reasons- 
First, the fauna may have migrated into the region in which the Ham- 
ilton formation was deposited, in which case the fauna existed prior to 
the beginning of that formation; second, unless evidence can be fur- 
nished of the destruction of the fauna at the time of the deposition 
of the Tully limestone or the Genesee shale, there is no reason to 
believe that its integrity as a fauna was there suddenly lost. But we 
may assume that evidence of lessening bionic value of these species, as 
indicated by their loss of dominance in the local or temporary faunules 
