GEOLOGY OF THE PENN YAN-HAMMONDSPORT QUADRANGLES 45 



It is exposed in the Big Stream gorge west of the Northern Cen- 

 tral Railroad bridge, where it is a band of thin limestones and 

 shales 5 feet thick overlain by the Rhinestreet black shale, the 

 intervening light shales having thinned out and disappeared. 

 Fossils are much less common in the Parrish limestone, on this 

 quadrangle than in the Naples valley. 



Manticoceras pattersoni Hall, Tornoceras 

 uniangulare Conrad, Probeloceras lutheri Hall 

 and Orthoceras pacator Hall are the more common 

 cephalopods and Styliolina fissurella Hall is abund- 

 ant. 



The Cashaqua beds are 230 feet thick on the Naples quadrangle. 

 They are increased toward the north and east by the assimilation 

 of the upper part of the Middlesex shales and lose by the thinning 

 out of the soft shales between the Parrish limestone and the Rhine- 

 street shale. The formation reaches its greatest thickness, 250 

 feet, in the region northwest of Penn Yan, and, decreasing gradually 

 toward the southeast, is 207 feet thick in the vicinity of Watkins. 

 Fossils are rare in the lower part of the Cashaqua beds, but occur 

 in considerable numbers in a few layers, mostly in the upper part, 

 of soft light colored shales. The fauna in this vicinity consists of 

 species of 4 crustaceans, 16 cephalopods, 5 pteropods, 12 gastro- 

 pods, 25 lamellibranchs, 4 brachiopods, 1 coral, 1 crinoid, 3 plants. 



The more common of these fossils are: 



Spathiocaris emersoni Clarke 

 Manticoceras pattersoni Hall 

 Probeloceras lutheri Clarke 

 Tornoceras uniangulare Conrad 

 Hyolithus neapolis Clarke 

 Phragmostoma natator Hall 

 Loxonema noe Clarke 

 Paleotrochus praecursor Clarke 

 Pterochaenia fragilis Hall 



Buchiola retrostriata v. Buch. 



Ontaria suborbicularis Hall 



O. clarkei Beushausen 



Lunulicardium acutirostrum Hall 



L. ornatum Hall 



L. hemicardioid.es Clarke 



Honeoyea major Clarke 



H. erinacea Clarke 



Aulopora annectens Clarke 



Plumalina plumaria is common in a 5 inch layer of shaly 

 sandstone exposed in a small ravine west of the rock cut of the 

 Northern Central Railroad 2^ miles southeast from Penn Yan. 

 See Museum bulletin 63 for full list of fossils. 



Rhinestreet shale 



This formation is a bed of black shale that overlies the Cashaqua 

 shale from the Seneca lake valley where it is but 1 foot thick to the 

 shore of Lake Erie in the town of Evans, Erie co., where it attains 

 a thickness of 185 feet. It is 3 feet thick on the east line of these 



