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ANNALS NEW YORK ACADEMY OF SCIENCES 
to the southward and are more comparable to the faunas at Clouderoft, and 
in the Hueco limestone. This phenomenon may result from several causes, 
— to a change of facies at the same horizon, or the introduction of different 
facies at new horizons, etc., but in any event, if the fact thus suggested is 
substantiated, it seems to render untenable the proposition that the peculiar¬ 
ities of the Guadalupian fauna are due to position in time, which I had 
employed as a working hypothesis, and of course to make it necessary to 
abandon the tentative correlations which developed from it. The alterna¬ 
tive hypothesis that this facies, remarkable as it is, is due to local conditions 
would be demanded by the evidence. 
On this new interpretation it becomes extremely difficult to determine any 
exact relationship between the trans-Pecos section and that of the Mississippi 
Valley. The unique character of the Guadalupian fauna, which at first 
suggested that it belonged to a later period than any of the Carboniferous 
faunas of the Kansas section, at least effectually precludes a correlation 
with that section by means of faunal evidence at present known. A few 
genera, such as Enteletes, have a characteristic range in the Kansas beds, 
but they are either absent from the Guadalupian fauna, or, if present, as is 
the case with the genus mentioned, their evidence can hardly be relied on. 
The influences which made so many of the Guadalupian genera and practi¬ 
cally all of the species different from those of Kansas and even segregated the 
species of the common genera into altogether different types would hardly 
maintain the ranges of those genera at the same level but would extinguish 
them earlier or later in one region or the other. At least the hypothesis of 
uniformity appears the more improbable. 
The typical Hueconian fauna while, as already remarked, it shows far 
more resemblances than the Guadalupian to the Pennsylvanian faunas of 
the Mississippi Valley, is yet much more Russian than American in its 
facies. I noted in my Guadalupian report that it was reminiscent of the 
earlier rather than the later faunas of the Kansas section, but it also affords 
no basis for definite faunal correlation. The same is true of the more north¬ 
ern faunas into which Mr. Richardson’s work has shown that the Guada¬ 
lupian faunas are transformed or by which replaced. They have a western 
rather than an eastern facies and show nothing suggestively analogous to the 
Kansas faunal sequence. In a brief survey therefore of the faunas of the 
trans-Pecos region, I find no point d’appui in invertebrate paleontology for 
an exact correlation of the Guadalupian series with the Kansas section. 
It might correspond to one part almost as well as to another, or it might be 
above as was my original hypothesis. A fortiori, if the Guadalupian faunas 
do not maintain their characters for one hundred miles to the northward, 
at least as great or even greater transformation may be expected at equiv- 
