Handbook of Paleontology 393 



stone and calcareous concretions are common. These 

 lower calcareous beds have been called the Centerfield 

 limestone (Clarke '03). This horizon extends as far 

 west as Erie county and also has been traced eastward 

 to the type locality of the Hamilton in Madison county. 

 The Ludlowville shale has a thickness of about 60 feet 

 in the Buffalo area. The thickness increases eastward 

 to 125 feet in Ontario county and 350 feet or more in 

 Onondaga county. The Moscow shale formation con- 

 sists of soft, light bluish gray shales that are usually 

 somewhat calcareous and in some exposures show con- 

 tinuous concretionary layers crowded with fossils. This 

 shale has a thickness of 15 to 50 feet in the western part 

 of the State and thickens eastward to about 200 feet in 

 the central part. In western New York there lies be- 

 tween the Ludlowville and Moscow shales, as previously 

 defined, a limestone band I 1 /* to 2 feet thick that persists 

 eastward for more than a hundred miles. To this stra- 

 tum has been given the name Tichenor limestone (Clarke 

 '03) from the exposure at Tichenor point on the west 

 shore of Canandaigua lake, Ontario county. It carries 

 an abundant Hamilton fauna. Fifty to 75 feet above 

 the Tichenor limestone is another limestone layer lying 

 in the midst of the shale mass and designated the Menteth 

 limestone (Clarke and Luther '04) from Menteth point, 

 Canadaigua lake. The bed is noteworthy for the fine re- 

 placement of the fossils by silica. The "Encrinal lime- 

 stone" of Cayuga lake, as pointed out above, has now 

 been found to correlate farther west with the Menteth 

 instead of the Tichenor limestone, which eastward be- 

 comes shaly and disappears in the vicinity of Seneca 

 lake. This places the Tichenor limestone within the Lud- 

 lowville and makes the Menteth limestone the base of the 



