[Annals N. Y. Acad. Sci., Vol. XIX, No. 6, Part I, pp. 135-147. 27 December, 
1909.] 
THE GUADALUPIAN FAUNA AND NEW STRATIGRAPHIC 
EVIDENCE . 1 
By George H. Girty. 
When the Guadalupian fauna was described its stratigraphic relations 
were unknown, except with formations in the immediate vicinity. Even 
these were known chiefly to the south and west. In spite of this lack of 
stratigraphic data I felt compelled to consider in a tentative manner the 
relations of the Guadalupian fauna with the faunas of the Mississippi 
Valley, not only biologically but in the category of geologic sequence ; 2 
failure to do so would surely have been a source of criticism. The import¬ 
ance of the fauna and its affinities with those of Europe and Asia made it 
hardly possible to avoid this point, while the incompleteness of the data 
made it necessary to engage it with extreme caution. The evidence employed 
had, in the nature of the case, to be paleontological. 
One of the pivotal facts in the evidence, regarding which there can hardly 
be a difference of opinion, is that the Guadalupian fauna is within certain 
limits quite different from any faunas of the Mississippi Valley. Two 
interpretations could be given to this fact. Either it was due to environ¬ 
ment and the Guadalupian fauna was equivalent to some very different 
fauna in the Mississippi Valley, or it was due to time, and the Guadalupian 
fauna belonged to a horizon not represented by the faunas of that area. 
One explanation or the other it was necessary to adopt as a working hypothe¬ 
sis. The premise upon which the science of stratigraphic paleontology 
proceeds is, as is well known, that two horizons containing the same fauna 
should not be regarded as different, or two horizons containing different 
faunas should not be regarded as the same, unless substantial stratigraphic 
1 Published by permission of the Director of the U. S. Geological Survey. 
Read by title before the New York Academy of Sciences, 6 December, 1909. 
2 In his generous critique of my Guadalupian report Dr. J. W. Beede says, “It is very 
difficult to determine what Dr. Girty’s conclusion as to the relative age of the Guadalupian, 
Russian and Kansan deposits is” (Jour. Geol., vol. 17, p. 679. 1909). Dr. Beede seems to con¬ 
fuse my recognition that the opinion which I entertained on this point was not substantiated 
by conclusive evidence, and my feeling that it was necessary to discuss other hypotheses, with 
not having or not expressing any clearly defined opinion or hypothesis at all. The conclusion 
tentatively adopted was that outlined in the present paper and pretty clearly intimated on pp. 
42 and 50 of the Guadalupian report. 
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