II Ithaca Group ii 



About 600 feet of sandstone above the Naples beds are re- 

 ferred to the Portage. Only ten species have been found in 

 the fauna of these Portage sandstones, seven of which are com- 

 mon to the Chemung. 



It should be observed that * ' Naples beds' ' as used by Williams 

 and Clarke represent entirely different horizons. Prof. Williams, 

 who introduced the term, applied it to a horizon "about twelve 

 hundred feet above the highest Genesee slate."* Prof. Clarke 

 has applied the same term to a portion of Hall's Portage lying 

 diredtly above the Genesee; above the Naples beds of Clarke is 

 the Portage sandstone followed by the High-point bed, which 

 latter is equivalent to the Naples horizon of Williams. In order 

 to avoid confusion, the term Naples beds, if used, should at 

 least include the horizon originally designated by Williams. 



As regards the absence of the Ithaca fauna from the Upper 

 Devonian of western New York, the results of Prof. Williams' 

 studies of the Genesee se(5liont correspond with those of Clarke 

 and Williams in Ontario county. The fauna of the Portage 

 group of the Genesee se(5tion as given by Prof. Williams is very 

 meagre as compared with the Portage as developed at Ithaca, 

 while it contains some of the more chara<fleristic fossils found at 

 Ithaca, as Glyptocardia speciosa and Lunulicardium fragile. Most 

 of the species which at Ithaca are common to the Portage and 

 Ithaca groups are absent from the Portage of the Genesse sec- 

 tion. Immediately following the Portage, Williams finds the 

 typical Chemung fauna. The peculiarities of the Chemung 

 fauna immediatety above the Portage fauna indicate that it 

 represents a later stage than the Ithaca fauna. At Hornells- 

 ville, about half way between the Genesee and Cayuga sedtions", 

 Orthis tioga of the Chemung, and the Chemung stage of Spiri- 

 fer mesacostalis were found diredlly above shales carrying the 

 Portage Glyptocardia fauna. The occurrence in the western 

 sections, immediately above the Portage, of fossils of a type 

 which in the eastern sedtions were developed after the Ithaca 

 stage, indicates that in the west the Portage fauna must have 

 continued until after the close of the Ithaca stage in the east. 



Previous to his study of the Genesee se(5tion, Prof. Williams 

 made a comparative study of ten sections through the Upper 

 Devonian. These extended in an east and west diredtion from 



*Am. Jr. Sci., vol. xxv, p. 97, 1883. 

 tBull. U. S. Geol. Surv., No. 41. 



