Handbook of Paleontology 279 



ceding this which permitted the entrance of a marine 

 fauna. 



The. Normanskill shales (Ruedemann '01) are in part 

 equivalent in age to the Upper Chazy limestones but were 

 deposited in the Levis trough farther east. They were 

 named from the typical exposure at Kenwood, along the 

 Normanskill, a tributary of the Hudson river just south 

 of Albany (figure 36). They, too, are graptolite-bearing 

 shales formerly included in the old "Hudson River" 

 group. Two graptolite zones (8 and 9) are represented 

 in the Normanskill shales, that of Nematograptus gracilis 

 and that of Corynoides gracilis which is considered of 

 Black River age (Ruedemann). The formation contains 

 a large and cosmopolitan graptolite fauna. There are 

 probably 2000 feet of Normanskill shales which vary con- 

 siderably lithologically, for the most part, however, con- 

 sisting of dark gray to black argillaceous shales. Red and 

 green shales also occur, and the formation is particularly 

 characterized by heavy beds of white-weathering chert 

 (2-10 feet) and grit (2-30 feet). Above this last zone 

 in the Mohawk valley is a graptolite zone (10 Crypto- 

 graphs tricornis insectiformis) of Snake Hill (Trenton) 

 age which was formerly described as the Magog shales 

 and is now in process of revision (Ruedemann). The 

 Rysedorph conglomerate (Ruedemann '01) occurs in 

 Rysedorph hill (locally called Pinnacle or Sugar Loaf 

 hill) two miles southeast of Rensselaer (across the river 

 from Albany) , and overlies the Normanskill. It is a fine 

 collecting ground for fossils. The youngest pebbles are 

 of Trenton age, but faunas represented by the pebbles 

 range from Lower Cambrian to Trenton. Seven kinds 

 of pebbles have been found furnishing an amazingly rich 

 and strange fauna, with Atlantic elements hitherto known 



