1152 NEW YORK STATE MUSEUM 



In Ulster county there is a space above the Wilbur limestone 

 represented by the lower cement bed that, with the exception of 

 Leperditia, is almost nonfossiliferous, but, when the Cobleskill is 

 reached, we have again, in part, the Wilbur limestone fauna, but 

 with a less proportion of Niagara species and with an increase 

 of new forms that have not been observed in any formation below 

 the Cobleskill. 



In the 42 feet of shales and limestones below the Cobleskill of 

 the Nearpass section in New Jersey there occurs a fauna 

 which like that of the Wilbur limestone is Niagaran in charac- 

 ter. In the latter section however the cement bed, so conspicuous 

 below the Cobleskill, in Ulster county, is lacking, and the forma- 

 tion is more or less fossiliferous throughout. Some of the layers 

 in the New Jersey section are crowded with Leperditia strongly 

 suggesting brackish water conditions, but to a much less extent 

 than in Ulster county. 



The fauna of the Nearpass section has been studied with some 

 detail by Weller, 1 and he was able to identify with more or less 

 certainty 31 species that for the most part are well known 

 Niagara species. Some of the identifications as thus made by 

 Weller, presumably those of Niagara species, have been ques- 

 tioned by Ulrich and Schuchert; 2 but, judging from the fact that 

 we do have Niagara species below the Cobleskill in Ulster county 

 and relying on the previous work of Weller, it would not be 

 unsafe, I think, to assume that there is below the Cobleskill in 

 the Nearpass section, as in Ulster county, a fauna with unmis- 

 takable Niagara elements. 



One of the chief differences between the section in Ulster 

 county and the Nearpass section is the development in the former 

 of an extensive cement bed which is entirely lacking in the latter, 

 but is represented by shales and limestones. In the Ulster 

 county section the marine conditions during which the fauna of 

 the Wilbur limestone flourished seem to have been followed by a 

 period of nonmarine or brackish water conditions, during which 

 the overlying cement bed was formed. This change in conditions 

 of sedimentation caused an almost entire destruction of the fauna, 



1 N. J. State Geologist. An. Rep't. 1899. p.7-20. 

 a N. Y. State Paleontologist. An. Rep't. 1901. p.650. 



