IOWA ACADEMY OP SCIENCES. 
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chief of American paleontologists, the recent utterances of H. 
S. Williams* are full of meaning : ‘ ^ And now the modern school 
of paleontologists are demonstrating the fact that the divisional 
lines of the biologic or time scale do not correspond to those of 
the stratigraphic scale, but are determined by independent 
factors.” So diverse are the divisions suggested by the fossils 
in the time scale from those indicated by the stratigraphy 
in the formation scale, that the same author saw the necessity 
of a dual nomenclature; f of a distinct set of names for the 
members of the two scales. 
In this connection, also, there may be mentioned a discussion 
on the character of fossil evidence, by Brooks |. It is espe- 
cially noteworthy as coming from a biologist, and is from a 
standpoint that is not and cannot well be considered by 
the average paleontologist. Although it is not mentioned 
in the discussion, it may be inferred that the proof is con- 
clusive that the fossils do not indicate the great antiquity 
of life that they are generally thought to, as deduced from the 
chief argument: that at the time of the earliest Cambrian forms 
life was already fully nine- tenths differentiated. It is shown 
that differentiation of life goes on with great rapidity along the 
shore, and more or less independently in different localities, on 
account of the fierce struggle for existence. The suggestive - 
ness of the statement is startling; at a single stroke it prac- 
tically deprives the fossils of the greater part of their value as 
trustworthy elements for general correlation, and relegates the 
whole method to the same rank as correlation by lithology, or 
similar succession. The recent trend of paleontological 
progress has been rapidly in the direction of biology, rather 
than towards geology, but the effect of Brooks’ suggestion 
is to remove it almost entirely from the latter field and to 
transfer it to the former. As in the case of certain of the 
other criteria of geological correlation, the usage of fossils 
becomes largely local. . 
The weakest point of all in general correlation by means of 
fossils is the great complexity of the problem surrounding dis- 
tribution of organisms in space. The intricacy of the laws 
governing the geographic range of animals and plants, at the 
present time, is only understood in the most general way and 
*U. S. GeoL Sur., Bull. 80, p. 267, 1891. 
tJournalGeolog-y, Vol. II, pp. 145-160, 1894. 
^Journal Geology, Vol. II, pp, 455-479, 1894. 
