GEOLOGY OF THE GENEVA-OVID QUADRANGLES 



21 



H. irregulare Hall 

 H. reflexum Hall 

 H. obconicum Hall 

 H. confluens Hall 



Amplexus hamilloniae Hall 

 Heliophyllum halli Edwards c'V 



Haime 



Favosites placenta Rominger 

 F. arbusculus Hall 

 F. argus Hall 



Alveolites golclfussi Billings 

 Pleurodictyum stylopora Eaton 

 Striatopora limbata Eaton 



Tichenor limestone 



The thin, but widely extended stratum of limestone that separates 

 the Ludlowville from the Moscow shale was first described in the 

 Third Annual report of the Fourth Geological District for 1838, 

 page 298, by Professor Hall as it appears in Seneca county. In 

 that report it is considered as " the terminating rock of the shale 

 last described " (Ludlowville) under the designation Encrinal lime- 

 stone from the abundance of fragments of crinoidal columns it 

 contains. 



In the final report on the fourth district, page 187, it is described 

 as one of the divisions of the Hamilton group. The term " Tiche- 

 nor " was substituted for " Encrinal " in the title of this formation 

 in Classification of New York Scries of Geological Formations by 

 Clarke and Schuchert, 1900, from its well known favorable exposure 

 at Tichenor point, Canandaigua lake. 



This formation is a thin stratum of calcareous sediment that 

 varies in character from a light colored compact blue limestone a 

 few inches thick to a mass of hard calcareous shale with a thin 

 uneven limestone at the base and other thin lentils of similar charac- 

 ter interstratified in the succeeding 4 to 6 feet of shale. 



The compact layer has a subcrystalline appearance when broken, 

 due to the fragmentary crinoidal columns, and the surface is at 

 some localities marked by an abundance ofSpirifer granu- 

 losus, conspicuous for its great size. Otherwise this stratum is 

 not usually very fossiliferous, but the overlying shales are rich in 

 fine specimens of forms common in the shale above and below. 

 Among the fossils found in the Tichenor limestone are : 



Phacops rana Green Lyriopecten orbiculatus Hall 



Orthcceras coelamen Hall Spirifer granulosus (Conrad) 



O. exile Hall S. mucronatus (Conrad) 



The more favorable exposures of the Tichenor limestone on these 

 quadrangles may be found at the top of the lower falls in the 

 ravines of Bloomer falls and other creeks 2 miles east of llavt 



