332 New York State Museum 



Rochester region the shale is about 85 feet thick. Com- 

 plete exposures are found here in the Genesee gorge and 

 in the Niagara gorge (60 feet). The upper part of these 

 shales is lighter in color and characterized by the oc- 

 currence of thin layers of limestone, one to three inches 

 thick. This shale is known as far eastward as Oneida 

 county and probably extends into Herkimer county 

 where a similar shale occurs below the concretionary 

 layer of the Lockport dolomite. The lithologic change 

 from the Irondequoit limestone to the Rochester shale 

 is very abrupt, but there is a strong affinity between the 

 two faunas. The Rochester shale is very rich in fossil 

 remains. Fossils are abundant in the lower part of the 

 shales and crinoids here are among the most abundant 

 and characteristic forms (Caryocrinus (cystoid), Eu- 

 calyptocrinus, Ichthyocrinus, Lecanocrinus etc.). To- 

 ward the top fossils are less abundant and the upper few 

 feet are practically barren. Higher up the fossils are 

 chiefly bryozoans. More than 80 species of bryozoans 

 alone have been described from this fauna, about one- 

 third of the total number of species. A characteristic 

 form is Phylloporina asperato-striata. Besides the 

 crinoids and bryozoans, these shales abound in species of 

 corals (Enterolasma caliculum, Favosites), brachiopods 

 (Dalmanella elegantula, Nucleospira pisifo-rtnis, Stro- 

 pheodonta profunda, Rhipidometta hybrida, Orthis flab el- 

 lit cs, Plectambonites transversalis, Leptaena rhom- 

 boidalis, Rhynchotreta cuneata var. americana, Spirifer 

 niagarensis, Whit field ella nitida, A try pa reticularis), 

 pelecypods (Pterinea emacerata, Leiopteria sub plana), 

 gastropods (Platyceras niagarense, Diaphorostoma niaga- 

 rense) and trilobites (Calymenc niagarensis, Illaenus 



