PORTAGE AND NUNDA QUADRANGLES 5 1 



but since the erection of the dam below it only appears at the 

 west end of the highway bridge immediately north of the dam, 

 where the lower layers may be seen above the outcrop of black 

 Genesee slate previously mentioned. 



Fossils are abundant and peculiar, the purer limestone being 

 composed almost wholly of the minute shells of the pteropod 

 Styliolina fissurella (Hall) and the entire fauna has 

 very close relations with that peculiar to the Portage beds above. 

 It is the earliest appearance in New York of the Naples fauna or 

 the world-wide zone of Manticoceras intumescens. 



The following are common species, but for the full list with 

 descriptions and illustrations consult Naples Fauna in Western 

 New York, pt i and 2. 



Manticoceras pattersoni (Hall) var. Honeoyea styliophila Clarke 



styliophilum Clarke Buchiola retrostriata {v. Buck) 



Gephyroceras genundewa Clarke Pterochaenia fragilis (Hall) 



Tornoceras uniangulare (Conrad) Aulopora annectens Clarke 



Phragmostoma natator Hall Melocrinus clarkei Williams 



In the vicinity of these quadrangles favorable exposures of the 

 Genundewa limestone may be found in several ravines along the 

 west side of the Delaware, Lackawanna and Western Railroad 

 between Moscow and Greigsville, also at the top of the falls in the 

 Fall brook ravine at Geneseo and along the east and west road 

 ^ miles south of the same falls. 



It causes cascades in many ravines in Livingston and Ontario 

 counties and is well exposed in the bed of Murder creek at Gris- 

 wold, Wyoming co. 



West River shale 



A bed of dark to black shale about 100 feet thick succeeds the 

 Genundewa limestone in this section. The lower part is covered 

 by the water above the Mount Morris dam but the upper part is 

 finely exposed in the cliff on the east side of the mouth of the 

 gorge. 



For about 62 feet next above the limestone the shales are mainly 

 dark gray or blue black with thin layers of densely black and slaty 

 bituminous shale 4 to 6 inches thick occurring at intervals of 2 to 6 

 feet, producing in this and other cliffs of these beds a distinct 

 banded effect. 



These shales are contrasted with the Genesee shale below by 

 their generally lighter color and less bituminous character. They 

 are also more fossiliferous, though the number of species repre- 



