MARCBLLUS LIMESTONES AND THEIR FAUNAS 135 



far as Ontario county in a pure limestone sediment and perhaps 

 as far as Cayuga county with a more argillaceous sediment, and 

 was then driven back by the shallowing sea and the return of 

 the bituminous muds. Its western origin determines the same 

 derivation for the fauna of the great mass of calcareous and 

 sandy Hamilton shales^ which held the field for a long period 

 over the full width of the state, but was eventually driven out 

 of western New York by the invasion of a new western fauna, 

 heralded by the early intrusion of the worldwide brachiopod, 

 Hypothyris cub o ides, and immediately followed by the 

 outpouring of species constituting the fauna of the Manticoceras 

 intumescens zone (Portage stage). 



OTHER LIMESTONE BEDS IN THE MARCELLUS SHALES AND THEIR FAUNAS 



A noteworthy limestone layer has been recorded in the Livonia 

 -shaft section lying 27 feet below the Stafford limestone, the inter- 

 val being filled with black shales. This layer is 4 feet thick, the 

 upper 2 feet being impure and almost devoid of fossils, the low^er 

 being a quite pure limestone containing the following species: 



Phacops rana Green 



Orthoceras subulatum Hall 



O. incarceratum Clarke 



O. lima Hall 



Tornoceras uniangulare Conrad 



Tentaculites gracilistriatus Hall 



Pleurotomaria lucina Hall 



Aviculopecten cf. fasciculatus Hall 



Modiomorpha subalata 



M. concentrica Hall 



Gypricardinia indenta Conrad 



Microdon bellistriatus Conrad 



Nuculites oblongatus Conrad 



Palaeoneilo plana Conrad 



Tropidoleptus carinatus Conrad 



Spirifer audaculus Conrad 



Ambocoelia umbonata Conrad 



