70 NEW YORK STATE ^[USEUM 



waters of that time held approximately the same relative propoi 

 tions of salts, in solution as the ocean of the present day, their 

 evaporation would afford one part g}^psum to something over 20 of 

 salt. As gypsum occurs interbedded with the salt and probably 

 distributed moire or less through the Vernon shale below the latter, 

 this relative amount may well be present in its normal order. The 

 relations indicate, however, that the process of evaporation while 

 the first gypsum and salt were laid down was subject to frequent 

 vicissitudes from the influx of new supplies of sea water into the 

 basins. After the salt had been precipitated by repeated evapora- 

 tions the process was suspended for a time, during which the basins 

 were probably invaded by land drainage and shales were accumu- 

 lated in considerable thickness. A renewal of the early conditions 

 with a fresh supply of sea water started the precipitation of gypsum 

 again, but this time the process was not continued long enough 

 apparently to bring down salt, or if it were precipitated it was 

 redissolved before the overlying strata were formed. 



Both the salt and main gypsum beds maintain a constant horizon 

 throughout their extenit. The main gypsum beds are found only in 

 the Camillus shale and are generally limited to the upsper section. 

 In the western part of the State they are capped by limestone which 

 shows no evidence of alteration by ground waters, and there are 

 layers of unchanged limestone intercalated in the shale. There 

 seems to be no sufficient explanation for any selective action on the 

 part of the limestone whereby certain beds were more prone to alter- 

 ation than others. ■! 



3 In the discussion of the stratigraphy of the Salina stage it was 

 noted that the variations in the character of the strata are accom- 

 panied by marked fluctuations in the abundance of fossil remains. 

 The preceding Niagara stage is characterized by a fairly prolific 

 and varied fauna which has, however, a peculiar development that 

 is connected by paleontologists with changes of physical surround- 

 ings. The Pittsford sihale at the base of the Salina holds a very 

 different fauna that is characterized by eurypterids. Throiughout the 

 succeeding intervals represented by- the Vernon shale, salt and 

 Camillus shales, there is little or nothing to be found in the way of 

 fossil remains, and only with the Bertie waterlime, at the close of the 

 Salina, do they reappear and are then represented by an assemblage 

 related to that of the Pittsford shale. The lack of fossils in the 

 gypsum beds may be explainable, perhaps, as the result of solution 

 and breaking down of tlie strata by underground circulations, but 

 •this theory fails to account for their absence in the shales and un- 



