580 HENRY SHALER WILLIAMS 



of New York made by Messrs. Vanuxem and Hall, and regarded by 

 them as the standard section of the portion of the Devonian there 

 represented. The revision was based upon a critical study of the 

 composition, sequence, and range of the fossil faunas gathered in 

 constructing the folio map of the Watkins and Catatonk quadrangles 

 now in progress. The classification into taxonomic categories 

 (i. e., series, formations, members, and lentils) is in accordance 

 with the rules of classification and nomenclature of the United 

 States Geological Survey as published in the Twenty- fourth Annual 

 Report for 1902-3. 



The Nunda {shale and flagstone) formation is the stratigraphic 

 equivalent of the Portage or Nunda group of Hall, the standard 

 section of which is in the Genesee valley; the term "Portage" having 

 been dropped from the name because it was already specifically 

 applied to the upper sandstone member of the Nunda formation 

 of the Genesee valley. The lithologically discriminated members 

 (Cashaqua, Gardeau, and Portage) there recognized are not dis- 

 tinguishable in the Ithaca section, which is divided into the Sher- 

 burne flagstone, the Ithaca shale, and the Enfield shale members. 

 The term "Enfield" is applied to the latter member for the town 

 of Enfield, where its typical exposures are found. 



The boundary between the Nunda and Chemung formations 

 is established on the generic change in fossils taking place at the 

 horizon indicated. The more prominent of the new genera first 

 appearing in the Chemung of this section are Dalmanella, Douvillina, 

 and the species Spirifer disjunctus. 



The Cayuta shale member contains the typical Chemung fauna 

 of Chemung Narrows; and the name "Cayuta" is apphed for 

 Cayuta Creek along the sides of which, from Cayuta Lake to its 

 discharge into the Susquehanna River, the typical exposures are 

 met with. The upper boundary of the Cayuta member is marked 

 by the fourth (above the Hamilton), and highest at present known, 

 zone of Tropidoleptus carinatus, called the Swartwood Tropido- 

 leptus zone for its conspicuous outcrop southwest of Swartwood at 

 about 1,600 feet altitude above sea-level. 



The second member of the Chemung formation is named the 

 "Wellsburg sandstone member" for its outcrop from Wellsburg 



