1158 NEW YORK STATE MUSEUM 



faunas of the Rondout and the Manlius, and this relation is 

 expressed chiefly by the passage of Eurypterus up into the 

 Manlius limestone. 



Hall 1 early called attention to the finding of " a specimen con- 

 taining a part of the head of a Eurypterus and several impres- 

 sions of a spirifer peculiar to the tentaculite limestone. The 

 character of the rock is intermediate in color, texture and com- 

 position, between the ordinary drab colored layers of the Onon- 

 daga salt group, and those of the tentaculite limestone." It is 

 possible that the above specimen may have been obtained from 

 the Rondout. Dr Clarke, however, has recently informed me 

 that he has found Eurypterus in the blue layers of the Manlius 

 limestone in Herkimer county. In Onondaga county, above the 

 blue layers containing the typical Manlius limestone fauna there 

 are two layers of " Waterlime " from which the original " water- 

 lime of Manlius " takes its name. From the upper layer of this 

 waterlime Luther 2 obtained a segment of a Eurypterus, showing 

 that these interesting creatures continued their existence through 

 all of late Siluric time, and that in this section at least there was 

 an alternation in the character of the sediments and, as sug- 

 gested by the fauna found in them, a considerable variation in 

 the degree of the purity of the waters in which the sediments 

 were deposited. 



Culmination and decline of the Salina sea 



The occurrence of Guelph and Niagara species in the Cobleskill 

 at the close of the Salina is very suggestive. The limits of the 

 Salina deposits as now known are marked faunally by lower and 

 upper Eurypterus beds, signifying that the period opened and 

 closed under similar physical conditions. If, however, we start 

 at the close of the Niagara period, we find the first indication of 

 increasing salinity, and with this change came the Guelph 3 fauna. 

 With the ever increasing salinity of the waters the Guelph fauna 



1 Palaeontology of New York. 1852. 2:339. 



2 N. Y. State Geologist. 15th An. Rep't. 1898. p.268. 



3 This fauna, together with the environments under which it lived, has re- 

 cently been studied by Clarke and Ruedemann, and is described in memoir 5 of 

 the New York State Museum. 



