35^ NEW YORK STATE MUSEUM 



the lower cement bed. A good view of the falls is given by 

 Darton^ in his report on the Geology of Ulster county. At High 

 Falls the thin layer above referred to contains unmistakable Decker 

 Ferry species, the most characteristic of which is M o n o t r y p a 

 corrugata Weller. The fauna obtained follows : 



1 Favosites sp. | 5 Orbiculoidea cf. tenuilamellata 



2 Monotrypa corrugata Weller 



3 Atrypa reticularis Linne 



4 Pterinea emacerata Conrad 



Hall 

 6 Orthoceras sp. undet. 



The study of the sections at High Falls and Accord and a 

 comparison of them with the sections farther south indicate 

 quite clearly that the lower cement bed at Rosendale and the 

 lower cement bed and Wilbur limestone at High Falls are of 

 the same age as the Decker Ferry formation as developed to the 

 southwest of these localities. It is also believed that the 

 cement bed which holds the stratigraphic position of the Bertie water- 

 lime of western New York is of the same relative age as the latter, 

 both underlying the Cobleskill limestone. In western New York 

 the Bertie limestone is characterized by an Eurypterus fauna. The 

 absence of Eur}^pterus from the formation in eastern New York is 

 attributed to the fact that this section of the State belonged to 

 another sea-province. We therefore propose to meet this difference 

 in -the east by introducing for the lower cement bed in Ulster and 

 adjoining counties the term Rosendale cement. The transition to 

 the Cobleskill from the underlying fossiliferous beds in eastern New 

 York has been shown. In western New York the transitional fea- 

 tures are somewhat more complex and obscure. Still enough is 

 known to show an intimate relationship between the Cobleskill and 

 Bertie formations. 



In the Eurypterus-bearing waterlime beds of western New 

 York (Bertie) Cobleskill fossils are rarely found associated with 

 Eurypterus. However Orthothetes interstriatus 

 Hall and Leper ditia scalaris Jones are occasionally 

 found on the same slab with Eurypterus. In beds which are 

 strictly referable to the Cobleskill and which contain Cobleskill 

 fossils the writer has never found an Eurypterus. The condi- 



'N. Y. State Geol. 13th An. Rep't. 1894. pi. to facing p.342. 



