20 NEW YORK STATE MUSEUM 



teth points below the Tiebenor limestone, and from Tichenor 

 point northward there are several small outcrops along the 

 Slide hill as far as Hope point and over the region to the west- 

 ward; Iving just at the lower declivity of the rise of land the 

 rock appears where the drift mantle is thin. 



This mass of sediments is probably equivalent in part to the 

 LudloivviUe sliaJcs of Hall, but at Ludlowville a limestone called 

 by Hall the Encrinal limestone was taken ia,s a line of division 

 between the shale masses, the upper being called the Moscow and 

 the lower the Ludlowville. It is yet to be determined whether that 

 Encrinal limestone is continuous with the Encnnal or Tichenor 

 limestone of the section under consideration and for the present 

 we can not employ here the name Ludlowville with entire security. 

 Hence the term Ganandaigua shale is employed on behalf of 

 more accuirate, though perhaps provisional expression. 



Tichenor limestone 

 This name is applied to a compact layer of hard bluish gray 

 often crinoidal limestone which has a thickness of about 1 foot. 

 It is separately designated for the reason that it is a continuous 

 formation across this area and Avell to the east and west beyond it. 

 It contains some of the characteristic fossils of the rock but they 

 are not specially abundant and are frequently replaced by depo- 

 sitions of strontianite. This rock has been commonly known as 

 the Encrinal limestone, a name applied to it by Hall as long ago 

 as 1839 and has been used by many writers in application to 

 limestone layers lying at actually distinct horizons in these rocks, 

 specially from the meridian here under consideration to Lake 

 Erie. On comparison of this section with that on Cayuga lake 

 where the Ludlowville shales were originally defined and the typi- 

 cal exposure of the Encrinal limestone was located, it was found 

 that there is no concurrence in the horizons indicated there and 

 here by the same term. In view of the various limestone strata 

 that have been referred to under this name and its extraordinarily 

 frequent employment throughout all geologic formations with a 

 great variety of stratigraphic meanings, it is best to abandon the 



