GEOLOGY OF THE PENN YAN— HAMMONDSPORT QUADRANGLES 49 



the State and is much emphasized east of the Naples quadrangle. 

 The estimated thickness of the Grimes sandstones on these quad- 

 rangles is 75 feet. It is not of great importance here except as a 

 bench mark but at Naples it is a prominent feature in the stratig- 

 raphy of the Portage rocks, producing high falls in the Grimes, 

 Tannery and Parrish gullies, and escarpments on the hillsides. It 

 is important there also as marking the close of the period during 

 which sediments carrying the Naples fauna were laid down, and 

 containing the earliest representatives of the Ithaca fauna in that 

 locality. 



On the Watkins and Elmira quadrangles those faunas are inter- 

 mingled in these beds, and it is probable that the same condition 

 obtains here. 



The following species have been found in the horizon of the Grimes 

 sandstones in the western part of the Penn Yan quadrangle or at 

 Naples : 



Protonympha devonica Clarke L. quadricostatum Hall 



Schizophoria impressa Hall Leptostrophia mucronata V anuxem 



Productella spinulicosta Hall Chonetes lepidus Hall 



P. lachrymosa Hall Ambocoelia umbonata Conrad 



Spirifer mesacostalis Hall Dictyospongia haplea Hall & Clarke 



Atrypa spinosa Hall Orbiculoidea sp. 



Liorhynchus mesacostale Hall Paropsonema cryptophyum Clarke 



The horizon is exposed on the Watkins quadrangle along the 

 Johnson Hollow creek, 1 mile west of Lower Pine valley and there 

 contains : Manticoceras pattersoni Hall ; Orthoc- 

 eras sp.; Buchiola retrostriata von Buch ; P h r a g - 

 mostoma natator Hall ; Paleoneilo filosa Conrad ; 

 Nuculites oblongatus Conrad; Grammysia sp., 

 together with Orthis tioga Hall ; Chonetes scitulus 

 Hall ; Schizophoria impressa Hall and Productella 

 spinulicosta Hall. 



There are good exposures of the Grimes sandstones in the ravine 

 in the western part of Hammondsport and that i mile south of the 

 village ; also in the upper part of the Wagener ravine. 



Besides the exposures mentioned at Naples the Grimes sandstones 

 may be seen in the cliffs at St Helena and at the mouth of Wolf 

 creek in the Genesee River gorge and along the shore of Lake Erie 

 between Silver Creek and Dunkirk. 



West Hill flags and shales 



The rock of this division consists of numerous thin, uneven flags, 

 2 to 4 inches thick and occasionally compact, even, blue sandstones 



