Maryland Geological Survey 



115 



of strata immediately beneath it transitional between the Decker Ferry 

 and the Cobleskill. Both Weller and Hartnagel referred the Manlius, 

 Rondout, and Cobleskill of southeastern New York and northern New 

 Jersey to the Silurian System. 



These interpretations are exhibited in the following table : 







Weller, 1902 





Hartnagel, 1903 





Manlius 





Manlius 





Rondout 



Rondout 



c 

 3 



1 

 o 

 O 



II 



>^ 



1 



Rhvnclionella lamellata i^one, 

 25 feet 



Cobleskill, 10 feet 

 Transitional zone, 15 feet 



w 



Ptilodycta frondosa zone 

 Chonetea jerseyensis zone 



a 



Rosendale 

 Wilbur 







Bossardville limestone 





Bossardville limestone 



The correlation of the Keyser of Maryland, with the Decker Ferry, 

 Eondout, and Manlius of northern New Jersey, has been considered 

 already. If Hartnagel's correlation of the latter formations be accepted, 

 the Keyser of Maryland represents the interval from the Wilbur to the 

 Manlius of southeastern New York, inclusive. 



Correlation with, Formations West of tJie Helderherg Mountains. — Hart- 

 nagel who has recently made a critical study of the Upper Silurian of 

 New York considers the Manlius, Eondout, and Cobleskill of southeasteni 

 New York equivalent to the formations bearing the same names in the 

 central part of the State.' Ulrich has recently presented a view that 

 differs widely from that of Hartnagel and Clarke and others." 



^ N. Y. State Mus., Bull. No. 69, 1903. 



' Pawpaw-Hancock Folio, U. S. Geol. Surv., 1912, Field Edition, pp. 62-65. 

 The writer is greatly indebted to Dr. Ulrich for revision and correction of the 

 accompanying statements 



