50 NEW YORK STATE MUSEUM 



large flat plates. Spherical concretions are common throughout 

 the Genesee shale. 



Fossils are very rare in this formation, specially in the more 

 bituminous beds. Drifted land plants and conodont teeth some- 

 times occur in the black shale, and the more calcareous layers to- 

 ward the top contain: 



Pleurotomaria rugulata Hall Orbiculoidea lodensis {Vanuxem) 



Styliolina fissurella (Hall) Liorhynchus quadricostatus Hall 



Pterochaenia fragilis (Hall) Probeloceras lutheri Clarke 



Lingula spatulata Hall Bactrites aciculum (Hall) 



The entire section of the Genesee slate is well exposed in several 

 ravines north of Moscow and in the Fall brook ravine at Geneseo 

 below the top of the falls and in numerous other localities along 

 its line of outcrops, which extends from Chenango county to Lake 

 Erie. 



Genundewa limestone 



The stratum of impure limestone referred to by Hall as suc- 

 ceeding the Genesee slate in the vicinity of Moscow and Geneseo, is 

 the heaviest of a series of similar character that seems to have 

 escaped farther notice until 1882, when it was described by Clarke, 

 in United States Geological Survey bulletin 16, as the " Styliola 

 band." 



In New York State Museum memoir 6, Naples Fauna in West- 

 ern New York, pt 2, Clarke, 1903, and in Bulletin 63, Clarke and 

 Luther, 1904, it is more fully described as a unit of sedimentation in 

 the Genesee beds and designated Genundewa limestone on account 

 of its very favorable exposure at Genundewa Point on the east side 

 of Canandaigua lake. 



This horizon is quite calcareous and concretionary as far east as 

 Cayuga lake, but the limestone first appears as distinct layers in 

 Gorham, Ontario co., when westward it is continuous to Lake Erie, 

 its peculiar structure making it easy of recognition wherever ex- 

 posed. 



In the Genesee valley region it is composed of five layers of dark 

 gray bituminous limestone from 2 to 14 inches thick separated by 

 layers of dark shale from i to 6 inches thick. Some of the lime- 

 stones are even and flaggy, while others are concretionary and the 

 laminations of the intervening shale are bent to conform with their 

 very uneven surfaces. 



The entire band was formerly exposed, at the west end of the 

 Pennsylvania Railroad bridge over the river at Mount Morris, 



