C. Schuchert — Pre- Cambrian Nomenclature. 475 



Art. XLVIII. — On Pre-Cambrian Nomenclature; by 

 Charles Schuchert. 



During the past ten years there have appeared a number of 

 most excellent studies on the structure and correlation of the 

 pre-Cambrian rocks of the Canadian Shield and the Lake 

 Superior region. To get these results in such form that under- 

 graduate students in geology could easily understand the 

 broader sequence of events, the writer asked his colleague, 

 Professor Barrel 1, to set them forth in the shape of a geologic 

 time-table.* We held that this classification " must be regarded 

 as provisional only, another step toward a larger and more 

 accurate knowledge of the long eons which preceded the fos- 

 siliferous record " (p. 17). Since then other classifications 

 have appeared, and the one by Professor Lawsonf stimulates 

 the writer to the following remarks. 



The writer admits that he has no knowledge at first hand 

 regarding the pre-Cambrian rocks but he is nevertheless 

 deeply interested in the wisdom unearthed by those capable of 

 working in this exceedingly difficult field. Some of this 

 knowledge he is called upon each year to present to students 

 in his course in Historical Geology. In this paper the writer 

 will limit himself entirely to the terminology, and more espe- 

 cially to the primary terms, the eras. As for the nomenclature 

 of these ancient times, the paleontologist is as well trained to 

 look into it as is the geologist, and it is therefore beside the 

 mark for Lavvson to state that " the paleontologists should 

 refrain from insisting on their nomenclature in a field in which 

 they do no work " (19). The rules relating to nomenclature 

 apply to all geologists, and if any one has constructive idea& 

 that will help to build up a better geologic time-table, it is his. 

 duty to present them to his colleagues. As for " insisting on: 

 their nomenclature," we are all bound to observe the rules of 

 nomenclature and to accept that which is well done. 



In regard to rules of nomenclature, Weeks in his North 

 American Geologic Formation Names% states : " In determin- 

 ing the names to be applied to formations the laws of priority 

 and prescription (general usage) should be observed. The 

 name first given to a definite formation or series of strata 

 should hold, unless this name is superseded in literature by 



* Schuchert and Barrell, A revised geologic time-table for North America. 

 This Journal, (4) xxxviii, 1-27, 1914. 



f A. C. Lawson, The correlation of the pre-Cambrian rocks of the region- 

 of the Great Lakes. Univ. Calif. Pub., Bull. Dept. Geology, x, No. 1, 1-19, 

 1916. 



JF. B. Weeks, Bull. 191, IT. S. Geol. Surv., 1902, 11. 



Am. Jour. Sci. — Fourth Series, Vol. XLII, No. 252. — December, 1916. 

 33 



