IOWA ACADEMY OF SCIENCES. 143 



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;! 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., BuU. 80, p. 267, 1891. 

 +Journal Geology, Vol. II, pp. 145-160, 1894. 

 Uournal Geolog-y, Vol. II, pp, 455-479, 1894. 



