Williams.] FAUNAL DISSECTION OF THE DEVONIAN. 43 
identity of the formations containing them. In other words, it had 
been assumed that for purposes of classification in the time scale the 
formation and the fauna are identical. The way in which fossils 
have been customarily labeled has prevented a testing of the truth of 
this assumption. If there be any distinction in time value between 
the formation and its fauna, it is difficult to demonstrate it so long as 
the only name and designation of the fauna is that of the formation 
in which it was originally found. 
If the "Chemung formation "be extended below the fossiliferous 
strata of Ithaca, as it was in the literature before 1880, then the 
fossils in the "Ithaca group" belong to the Chemung fauna. When 
the Ithaca fauna was dissected and it was shown that the species 
were not those of the Chemung fauna above, but were rather modified 
successors of the Hamilton fauna/ it became clear that, faunally, the 
Ithaca group was not a part of the Chemung formation. Neverthe- 
less, the term "Chemung" was still retained in general literature for 
the "period" which included both the "Ithaca" and "Chemung" 
epochs, so that the real issue was still obscured by the imperfection 
of the nomenclature which used " Chemung" with two meanings/' 
The terms "Portage," "Hamilton," "Trenton," and "Niagara" are 
also applied in this double sense in the classification of formations, 
making it almost impossible to frame a statement which will express 
the thought that formations and faunas are discriminated upon dif- 
ferent bases and that their limitations may not be identical. 
In order to demonstrate the actual facts in the case, it has been 
found necessary to collect a large number of statistics regarding the 
actual faunal contents of each zone in some well-known formation, 
and also regarding the separate faunules taken from outcrops of the 
same formation over an extended area. 
This work of dissecting and analyzing the faunas of the Devonian, 
begun in 1881, has been carried on continuously since that time. 
Students in the laboratory, at both Cornell and Yale, have been trained 
to discriminate, collect, and analyze the faunules, and to observe 
accurately the range and distribution of every fossil coming to their 
notice. Others outside have adopted the method, and, thanks to the 
painstaking and energetic labors of many workers, it is now possible 
to demonstrate from the statistics already gathered at least the dis- 
tinction between a lithological formation and a fossil fauna. 
It is now possible to state that the Tropidoleptus fauna of the Ham- 
ilton formation persists in its integrity above the top of the Hamilton 
formation; that in eastern New York it occupies a place in the 
column which is occupied in central New York by the Ithaca forma- 
tion and in the Genesee Valley by a portion of the Portage formation. 
«On the fossil faunas of the Upper Devonian along the meridian of 76° 30', from Tompkins 
County, N. Y., to Bradford County, Pa., by Henry S. Williams: Bull. U. S. Geol. Survey No. 3, 1884. 
*>See Manual of Geology, by James D. Dana, 4th edition, 1894, p. iU\. 
