588 HENRY SHALER WILLIAMS 



unity of the fossil fauna of the three subdivisions of the original 

 Portage or Nunda group, the definite change in faunal composition 

 passing on downward into the Genesee, and that observed on passing 

 upward into the Chemung in the region of the original section, 

 together give ample reasons for regarding this subdivision as a 

 "formation" in the technical sense of the rules. Each of the parts, 

 Cashaqua, Gardeau, and Portage, naturally falls into the nomen- 

 clature of "member" as defined in rule 5. 



The name of the formation. — There is thus a formation composed 

 of three members already described in the section of the Fourth 

 District of New York to which a definite name was applied by Hall, 

 but to the final adoption of the names of the subdivisions of the 

 Ithaca section rule 7 applies. Rule 7 reads: 



In the application of names to members, formations, and larger aggregates 

 of strata the law of priority shall generally be observed, but a name that has 

 become well established in use shall not be displaced merely on account of 

 priority. 



It is well known that the name "Portage" has been largely used 

 for the Portage or Nunda group; there is therefore some question 

 as to the proper name to apply to the formation. Hence, the rule 

 of common-sense must be called into use. Since the rules contem- 

 plate the application of distinctive terms to formations, as well as 

 to members and larger aggregates of strata, it is clear that the same 

 geographic part of the name cannot be applied distinctively to two 

 separate subdivisions. The law of priority applies to Portage as 

 the distinctive name for the upper sandstone member of the Portage 

 or Nunda group; this excludes the use of the abbreviation of the 

 group name to Portage by dropping from it the words "or Nunda. " 

 It is therefore proposed to rectify the usage by taking the second 

 of the synonymous geographic terms, and omitting "Portage or," 

 from the original name, to leave Nunda as the geographic part of 

 the formation name. Thus the revised nomenclature for Hall's 

 "Portage or Nunda group" is "Nunda formation," composed, in 

 the Genesee section, of the Cashaqua shale, Gardeau flagstone, 

 and Portage sandstone members. 



The Nunda formation in the Ithaca section. — A critical examina- 

 tion of the Final Reports of the Third and Fourth Districts indicates 



