4S4 C. Scfmchert — Pre- Cambrian Nomenclature. 



Agnotozoic as the equivalent of Paleozoic, Mesozoic, Cenozoic, 

 to cover this great group is a conservative one. Irving fore- 

 saw that the term would be objected to because sooner or later 

 the life will become to a greater or less degree known, and he 

 suggested as an alternative for Agnotozoic, Eparchean in 

 contradistinction to Archean, which was reserved by him to 

 cover the fundamental complex. As the character of the life 

 of this group is already beginning to be known, it seems to me 

 that the terra Proterozoic, considered for the place by Irving, 

 but rejected, is preferable to either Agnotozoic or Eparchean." 



We, therefore, see that the name Proterozoic has not been 

 defined and furthermore that it is synonymous with Agnotozoic, 

 a term in good standing. If the pre-Cambrian rocks are 

 separable into three eras, and it so appears to the writer, then 

 it would seem that Agnotozoic should be applied to that inter- 

 val between the Lauren tian and Algomian granites. If, how- 

 ever, there are only two eras, it should refer to the second one* 

 that following the Archeozoic. In any event, it should be 

 applied to the greatest series of pre-Cambrian clastic rocks 

 younger than the Archeozoic. 



In regard to the term Algonkian, it appears to have no 

 standing at all, since it is a substitute for and a synonym of 

 Agnotozoic, as stated by Dana, and Ohamberlin and Salisbury.* 

 The term Algonkian is usually ascribed to Walcott,f and while 

 he did use it first in print, in 1889, he did not define it. It 

 appears that Director Powell was the first to define Algonkian, 

 as follows :\ " This series of rocks [in the Lake Superior 

 region] lies beneath the Cambrian and above the Archean, and 

 represents a period of the earth's history during which lowly 

 forms of life doubtless existed, but left few definite traces of 

 their existence in the form of fossils. . . . The name ' Agnoto- 

 zoic ' was . . . designed as one of the greater terms of geologic 

 classification, coordinate with Paleozoic, Mesozoic, and Ceno- 

 zoic. In the geologic atlas of the United States such larger 

 classification will not be employed, but the largest time unit 

 recognized will be the period. At a recent conference of 

 geologists ... it was decided to make but one period of the 

 Agnotozoic, and the name ' Algonkian ' was chosen to designate 

 that period. It is not proposed to cancel the name Agnotozoic, 

 but to leave its use to students having occasion to employ 

 terms of higher classification." 



If there are three eras in pre-Cambrian time, and if the 

 lowest is to be known as either Archean or Archeozoic, the 



* J. D. Dana, Manual of Geology, 4th ed., 1896, 445 ; T. C. Chamberlin 

 and E. D. Salisbury, Geology, ii, 1906, 162. 



+ C. D. Walcott, this Journal (3), xxxvii, 383-384, 1889. 



jj. W. Powell, Tenth Ann. Rep., U. S. Geol. Surv., 1890, 20, 66; also 

 see VanHise, Bull. 86, U. S. Geol. Surv., 1892, 493. 



