New York State Museum 



'40). These beds which are represented in the east by 

 sands and arenaceous shales and in the west by black 

 shales, calcareous shales and limestones, are on the 

 whole richly fossiliferous. The Hamilton beds form a 

 thick wedge of clastic materials which thin westward with 

 numerous accompanying shifts or facies both in the 

 character of the rock and the fauna. Hall and Vanuxem 

 in their final reports included in this group the Skanea- 

 teles shale, Olive shale, Ludlowville shale, Encrinal lime- 

 stone and the Moscow shale. Dana enlarged the term 

 to include the Marcellus shales and the Tully limestone. 

 Until recently the term has been used to include every- 

 thing between the Cardiff shales and the Tully limestone, 

 that is, the Skaneateles, Ludlowville and Moscow for- 

 mations. Very recent studies of the Hamilton beds have 

 shown the necessity for some revision, and for the details 

 the student is referred to the paper embodying the re- 

 sults (Cooper '30). These studies have shown "that the 

 black muds of the Marcellus, often affiliated with the 

 Onondaga, thicken eastward and are gradually replaced 

 by gray arenaceous shale. Concordantly the Marcellus 

 fauna grades eastward into one of Hamilton aspect. 

 These phenomena have made it . necessary to place the 

 Marcellus formation in the Hamilton group, which, there- 

 fore, now consists in ascending order of the Marcellus, 

 Skaneateles, Ludlowville and Moscow formations. The 

 Skeaneateles formation and several members in the 

 higher formations show a similar westward shift of 

 faunal facies from one of Hamilton aspect in the east 

 to a modified Marcellus fauna in the west" (Cooper '29; 

 Geol. Soc. meeting abstract). It has also been found 

 that the Mottville limestone, regarded as the base of the 

 Skaneateles formation at its type section, is the equivalent 



