CAMBRIAN GEOLOGY AND PALEONTOLOGY 



II 



No. lo.— GROUP TERMS FOR THE LOWER AND UPPER 



CAMBRIAN SERIES OF FORMATIONS 



By CHARLES D. WALCOTT 



With the development of the mapping of the geological formations 

 of the United States, it has increasingly become evident that the use 

 of more than one term derived from the same geographic name is 

 faulty in principle and confusing in usage. I have long been guilty 

 of doing it in the use of Georgian for the Lower Cambrian series of 

 formations, and I now find that the name I derived Saratogan from, 

 for the L^pper Cambrian series, was previously used for the Cre- 

 taceous Saratoga formation. (See page 306.) Much as we may 

 regret the change to new terms, I think that in the long run of time it 

 will facilitate the understanding of the nomenclature of the Cambrian 

 system by the student. 



WAUCOBAN OR LOWER CAMBRL\N 



L'nder the principle stated in the preceding paragraph, the term 

 Georgian as used by me in 1891 ' is in bad form and should be re- 

 placed by a geographic name that has not been used for any geologic 

 formation or group of formations. The history and use of the name 

 Georgia is given in Bulletin 81, cited above, on pp. 98-113, 249-250, 

 and 360. 



Since the publication of Bulletin 81 in 1891, it has been found that 

 the greatest development of the Lower Cambrian terrane is in 

 Esmeralda County, Nevada, and the adjoining county of Inyo, 

 California. 



The Barrel Spring section of Nevada " has several thousand feet 

 of Lower Cambrian strata with a fine Lower Cambrian fauna. The 

 Waucoba"' section, 30 miles to the southwest in California, is also 

 finely exposed, and it has a well-marked Lower Cambrian fauna that 

 extends through 4,000 feet of strata. 



' Bull. U. S. Geol. Survey, No. 81, 1891, p. 360. 



' Smithsonian Misc. Coll., Vol. 53, No. 5, 1908. pp. 188-189. 



'Idem, pp. 185-188. 



Smithsonian Miscellaneous Collections, Vol. 57, No. 10 



305 



