Handbook of Paleontology 283 



pear in the cherty beds below, but the characteristic Low- 

 ville fossils have disappeared. The Lowville-Leray for- 

 mations are but slightly represented in the Champlain 

 valley ; there are intermediate beds representing the Low- 

 ville-Leray hiatus or unconformity of the northwest ; the 

 Watertown limestone is missing due to widespread uplift 

 at the close of the Leray. Subsidence followed in the 

 east with the accumulation of the Amsterdam limie stone 

 which is entirely absent in the west. The name was given 

 (Cushing '11) from the exposures at Amsterdam, Mont- 

 gomery county. It is the "Mohawk" limestone of Van- 

 uxem. This is a dark limestone like the Watertown with 

 a maximum thickness of 60 feet and carries about the 

 same fauna. 



The Trenton beds comprise limestones and shales and 

 sandstones. The Glens Falls limestone (Ruedemann '12), 

 named from the exposures at Glens Falls, Warren county, 

 has been determined to be of very early (basal) Trenton 

 age. It is well developed in the Mohawk and Upper Hud- 

 son valleys where it has a thickness of 17-40 feet. This 

 limestone is missing below the typical Trenton limestone 

 at Trenton Falls. Collections in this limestone show a 

 fauna including numerous brachiopods, abundant sea- 

 weeds, some trilobites and cystoids, as Pleurocystites. The 

 Trenton limestone (Conrad, Vanuxem '38) received its 

 name from the type section at Trenton Falls on West 

 Canada creek (figure 37). It is extensively developed 

 both to the west and east of the Adirondacks, but on the 

 south the formation is interrupted by numerous faults. 

 There is a rapid decrease in thickness of the Trenton 

 limestone eastward in the Mohawk valley and a rapid in- 

 crease of the shale in that direction. With the exception of 

 a bed of compact, barren limestone at the base the Trenton 



