330 New York State Museum 



above these beds represents the lower half of the Roches- 

 ter, leaving the overlying sandstones in the Clinton sec- 

 tion to represent higher parts of the Rochester. As stated 

 above, east of Clinton the overlapping of the Middle Clin- 

 ton by the Upper Clinton finally, in Herkimer county, 

 leaves the latter (as indicated by the fossils) and the 

 Oneida conglomerate as representatives of the Clinton 

 there. There is a decided faunal break between the 

 Middle and Upper Clinton in New York, as well as in 

 sections elsewhere, and the Rochester fauna is a mix- 

 ture of Atlantic and southern faunas. The Williamson 

 shale (Hartnagel '07) receives its name from the town 

 of Williamson in Wayne county, and is well developed 

 in this and Monroe county. In the Rochester section it 

 is represented by five or six feet of dark shale contain- 

 ing an abundance of Monograptus clintonensis, the most 

 characteristic fossil of the Williamson shale. It has not 

 been traced far west of Rochester. Eastward the shale 

 increases to its supposed maximum of 105 feet at Lake- 

 port (deep well) and then thins rapidly to the Clinton 

 section where it is thought to be represented by the 

 oolitic iron ore and the 18 feet of interbedded soft shale 

 and harder calcareous shale above the ore. The Wil- 

 liamson shales are greenish in color and there are a num- 

 ber of interbedded purple bands. These shales are quite 

 fossiliferous. Besides the graptolite the Williamson has 

 the first Clinton occurrence of the brachiopod Plectam- 

 bonites (probably P. elegantidiis) ; and a third charac- 

 teristic fossil is a supposedly new species of Ischadites 

 (plant?), conical or oval bodies, inclosing a central cavity 

 with a small summit aperture. The other fossils show 

 a decidedly closer alliance with succeeding Irondequoit 

 and Rochester species than with Middle and Lower Clin- 



