PORTAGE AND NUNDA QUADRANGLES 63 



contains 22 species of brachiopods among them S p i r i f e r 

 disjunctus Sowerby, besides many other forms, and another 

 lentil 3 miles south is a mass of fossil sponges and Chemung 

 brachiopods, forms that did not appear in the Genesee valley sec- 

 tion till after more than 200 feet of sediment had been deposited 

 above this horizon. The sandstones at the top of the formation 

 here pass gradually into soft sandy shales. The exact point of 

 contact with the succeeding formation is covered at Portageville but 

 is slightly exposed by the side of the Quarry hill road iy 2 miles 

 south of Nunda. The strata included in the Nunda sandstones as 

 considered in this bulletin have an aggregate thickness of 215 feet. 



In various recent publications the singularly interesting fact has 

 been brought to notice that an essential difference in classification 

 of the upper rocks of this Devonic series results from the inde- 

 pendent consideration of the stratigraphic and the paleontologic 

 evidence. In paleontology the Portage group here extends upward 

 to include a mass of olive shales with some sand having a thickness 

 of several hundred feet, and the upward extent of this fauna in the 

 Genesee section is characteristic of its range throughout the region 

 farther west in the State. But at the east, in the Canandaigua- 

 Naples meridian, this fauna disappears practically or entirely at a 

 horizon below that of the Nunda sandstones. These sandstones 

 have been traced almost foot by foot between these meridians, and 

 the stratigraphic continuity of the Nunda sandstones of the Genesee 

 section with the High Point sandstone of the Naples section is 

 beyond question. The seeming inappropriateness of a twofold 

 designation for the same geologic horizon is dispelled by the entire 

 difference in the contained faunas at these distant sections. In 

 paleontology the High Point sandstones carrying a brachiopod fauna 

 with Spirifer disjunctus are of Chemung age, the Nunda 

 sandstones of Portage age. We therefore have in the Nunda sand- 

 stones of the Genesee valley a member of the Portage group which 

 lies at the base of the Chemung group farther east. Another and 

 still higher member of the Portage group is also present in this 

 section and its presence and probable value were indicated by Hall 

 in 1839 [Annual Report, p. 392]. 



The two groups just described (Gardeau and Portage) occupy 

 a thickness of more than a thousand feet and are interposed 

 between the Cashaqua shale and the Chemung group. Indeed, 

 if we consider the Chemung group as commencing with the occur- 



