32 NEW YORK STATE MUSEUM 



the formation is characterized by the presence of this crustacean. 

 In the Hudson river valley about Rosendale, the lower waterlime 

 bed known as the Rosendale w^aterlime is found to occupy a 

 similar stratigraphic position, but herein no Eurypterus has been 

 found. The absence of these forms in the eastern section is 

 explained by the probability that between these two areas there 

 existed a land barrier, which prevented the migration from the 

 Salina sea lying west of the barrier. 



The Bertie waterlime varies in thickness in different sections. 

 Sixty feet are recorded from Canada, but in some places in New 

 York only lo feet intervene between the gypsum beds and the 

 Cobleskill limestone which lies just above. The portion just below 

 the Cobleskill is the i^art that is burned for hydraulic cement. The 

 hydraulic cement made in the vicinity of Buffalo and Akron is from 

 the Bertie. In Onondaga county considerable cement is made, but 

 from a higher horizon. The Bertie waterlime is also present in 

 Onondaga county, but it is not used to any extent for cement. 



Owing to the heavy drift covering, no outcrops of the Bertie have 

 been observed within the region mapped. It is present, however, as 

 shown by the adjacent sections. Just west from the southern por- 

 tion of the map, this formation is found overlying the gypsum bed 

 in the town of Wheatland. Here it has its characteristic drab color 

 and occurs in thin layers. Some of the layers contain fragments of 

 Eurypterus and large numbers of Leperditia scalaris are 

 found. Large hopper-shaped salt cavities also occur here. 



One mile west from Fishers, just east of the map, the Bertie 

 waterlime is seen in. the steep bank of the creek. A number of 

 fragments of Eurypterus were collected at this point. 



The presence of an extensive eurypterid fauna in this formation 

 is indicative of physical conditions similar to those during which 

 the Pittsford fauna lived. The formation in Erie and Herkimer 

 counties is noted for the abundance and fine preservation of these 

 crustaceans. 



The Bertie marks the last stage of the Salina sea which was 

 brought to a close by the invasion of the Atlantic waters. 



