Handbook of Paleontology 371 



Ulsterian, named from Ulster county; the Erian from 

 the Lake Erie section and in its strict sense including the 

 Hamilton beds and Marcellus shales (Clarke and Schu- 

 chert '99) ; the Senecan, from exposures in Seneca 

 county and the Chautauquan from exposures in Chau- 

 tauqua county. 



The Coeymans limestone (Clarke and Schuchert '99) 

 receives its name from the town of Coeymans, Albany 

 county. In the older reports it was known as the "Lower 

 Pentamerus" limestone from the most common brachio- 

 pod Pentamerus galeatus (now Sieberella coeymanen- 

 sis). This limestone extends farthest west of any of the 

 members of the Helderberg group, reaching the town of 

 Manlius in Onondaga county where it is overlain by a 

 thin representation of the Oriskany. The Coeymans 

 limestone has a maximum thickness of 50 to 60 feet (in 

 east central New York) and is the principal cause of 

 the Helderberg cliff (figures 51, 52) into which also 

 enters the underlying Manlius. It may be distinguished 

 from the Manlius by the bluish gray color, which 

 weathers light gray and the coarse granular texture. 

 The beds are massive, more so in the lower part, and 

 knotty, breaking up into irregular chunks. Shale part- 

 ings occur occasionally, also nodules and thin lenses of 

 chert. The Coeymans limestone is more silicious than 

 the Manlius and the shells and crinoid stems which it 

 carries tend to become silicified. The most common and 

 characteristic fossil is the brachiopod Sieberella coey- 

 manensis (Pentamerus galeatus), and next to this the 

 brachiopods Uncinulus mutabilis and Atrypa reticularis. 

 Other brachiopods reported from the Coeymans are 

 Stropheodonta (Brachyprion) varistriaia, Camwotoechm 

 semiplicata and Meristella laevis; pelecypods as 



