36 NEW YORK STATE MUSEUM 



The Trenton attains a maximum thickness of at least twenty- 

 feet with the summit not present as shown in the quarry one and 

 two-third miles east of Galway. The contact with the overlying 

 shale is nowhere visible so that any accurate determination of thick- 

 ness can not be made. 



Among the fossils noted in the Trenton limestone of the area are : 

 the coral — Monticulipora (Prasopora) lycoperdon 

 ( Say) ; crinoid segments ; bryozoa ; brachiopods — O r t h i s 

 (Dalmanella) testudinaria ( Dalman ) and Raf ines- 

 quina alternata ( Con.) Hall and Clarke ; gastropod — 

 Murchisonia bellicincta ( Hall) ; and the arthropod — 

 Trinucleus concent ricus ( Eaton) . 



In the Black River-Trenton area south of Broadalbin it is im- 

 possible to accurately place the boundary lines because of heavy 

 drift deposits, but this limestone is certainly present here between 

 the Little Falls dolomite on the east and the Canajoharie shale on 

 the west. Along the creek one-half mile north of Vail Mills frag- 

 ments of Lowville in the drift show nearness to rock in place and 

 in the quarry two miles south-southeast of Perth the rock is 

 exposed. 



CANAJOHARIE SHALE 



The shales of the lower Mohawk valley have recently been care- 

 fully studied by Doctor Ruedemann of the New York Survey and 

 certain important results which have been obtained will be pub- 

 lished in a forthcoming paper. Doctor Ruedemann has very kindly 

 given the writer advanced statements regarding the shales of the 

 Amsterdam-Broadalbin region and in a letter dated November 16, 

 1 910 he says: " The real Utica shale is in the lower Mohawk valley 

 underlain by about three hundred feet of black shale that has a 

 different fauna and belongs with the uppermost Trenton. This 

 shale I propose to call from its best outcrop the Canajoharie shale." 

 Heretofore all of the black shale of this region has been called 

 Utica. The shales of the southwestern portion of the Broadalbin 

 sheet, which rest directly upon Lower Trenton limestone, are cer- 

 tainly of Canajoharie age. 



The formation consists of dark gray to black, fine-grained, thin 

 and straight bedded shales usually rather calcareous, especially 

 toward the base. The dark color is due to the presence of finely 

 divided and partially decomposed organic matter, though nothing 

 like a workable coal bed is known to exist in the formation. 



