620 NEW YORK STATE MUSEUM 



The character of the fossils in this group of formations has 

 been fully discussed by Clarke. The fauna of the Portage series 

 as a whole is highly distinctive and not to be confused with that 

 preceding or with the Chemung fauna which follows. The lat- 

 ter is specially characterized by prevailing brachiopod types, a 

 group almost wholly wanting in the Portage, and per contra 

 the peculiar lamellibranchs and cephalopods of the Portage are 

 not carried over into the Chemung fauna save as one species or 

 another may have survived the general invasion of the Chemung 

 fauna from the east. 



In the town of Naples, about 30 miles east of the Genesee 

 river the upper beds of the Genesee shale, all of the Portage 

 divisions and several hundred feet of lower Chemung strata, in 

 the aggregate not less than 1500 feet, are abundantly exposed 

 in the numerous ravines and rock escarpments about the south 

 end of the Naples valley. 



In the strata above the Genesee shale the proportion of sandy 

 sediment, in the shape of flags and thin sandstones is noticeably 

 greater than in the Genesee river section, and the thickness of 

 the subdivisions is not the same, still the differences in litho- 

 logic character are so small, that no difficulty is experienced in 

 distinguishing the several subdivisions as previously described. 



The upper beds of the Genesee, succeeded by the band of 

 lighter colored shales and flags, and next above, the lower black 

 band are exposed along the road leading westward on the 

 Naples-Bristol town line near Woodville and near the mouth of 

 the Snyder gully, J mile south. 



The top of the Genesee shale in the road west of Woodville is 

 751' A.T. This point as indicated on the Naples sheet of the 

 topographic map is on the line of 42° 40' which crosses the 

 Genesee river 5 miles south of the mouth of the gorge at Mt 

 Morris and almost exactly at the place where the top of the 

 Cashaqua shale dips below the river level, which is here 602' 

 A.T. The top of the Genesee shale at Woodville is therefore 

 the difference in levels, 140 feet, plus the thickness of the 



