GEOLOGY OF THE PENN YAN-H AMMONDSPORT QUADRANGLES 53 



L. multicosta Hall 

 Atrypa reticularis Linne 

 A. hystrix Hall 

 Schizophoria impressa Hall 

 Orthis tioga Hall 

 O. carinata Hall 

 Stropheodonta cayuta Hall 



Leptostrophia perplana Conrad var. 



nervosa Hall 

 Stropheodonta demissa Conrad 

 Orthothetes chemungensis Conrad 

 Camarotoechia eximia Hall 

 Ambocoelia umbonata Conrad 

 Lingula spatulata Hall 



Chemung sandstones 



The Chemung sandstones and shales as defined in Museum bul- 

 letin 81 are the surface rocks over the high lands in the southern 

 part of the Hammondsport quadrangle, attaining in the extreme 

 southeast corner in the town of Hornby a thickness of 560 feet. 



They are almost entirely covered by a thin mantle of drift or dis- 

 integrated shale and sandstone, the few exposures being mostly the 

 results of grading the highways. They are, however, uncovered 

 sufficiently to show that, structurally, the formation is an aggre- 

 gation of light and dark shales and blue gray sandstones, much 

 like the West Hill flags and shales, except that many of the sand- 

 stones are laminated or schistose and light gray or almost white in 

 color. Calcareous lenses like those previously mentioned are more 

 frequent and usually more extensive than those below. 



Fossils are abundant at all horizons and in nearly all outcrops of 

 these beds, the more common species in this region being: 



Leptodesma longispinum Hall 



L. billingsi Hall 



L. shumardi Hall 



L. spiniger (Conrad) Hall 



L. disparile Hall 



L. matheri Hall 



Paleoneilo filosa (Conrad) Hall 



P. constricta (Conrad) Hall 



P. emarginata (Conrad) Hall 



Lyriopecten tricostatus Vanuxem 



Microdon sp. 



Liopteria chemungensis Vanuxem 



Mytilarca simplex Hall 



Grammysia sp. 



Pterinea chemungensis (Conrad) Hall 



Spirifer mesacostalis Hall 



S. marcyi Hall 



S. disjunctus Sowerby 



S. mucronatus var. posterus Clarke 



Productella lachrymosa Hall 



P. onusta 



P. hystricula 



Liorhynchus mesacostale Hall 



L. globuliforme Vanuxem 



Atrypa reticularis Linn? 



A. spinosa Hall 



Orthis tioga Hall 



O. carinata Hall 



Schizophoria impressa Hall 



Stropheodonta cayuta Hall 



Leptostrophia perplana Conrad var. 



nervosa Hall 

 Leptostrophia mucronata Vanuxem 

 Athyris polita Hall 

 Orthothetes chemungensis Conrad 

 Camarotoechia eximia Hall 

 C. contracta Hall 

 Ambocoelia umbonata Conrad 



