Maryland Geological Survey 117 



This conclusion is apparently further supported by the presence of 

 species related to those of the Cobleskill and Manlius of New York below 

 the base of the Chonetes jerseyensh zone in Maryland, including Tentacu- 

 lites gyracanthvs in abundance, Camaroiocchia ? lamellata, Camarotwchia 

 litchfieldensis, Stropheodonta hipartita, Leperdiiia alia, etc. Ulrich ex- 

 plains the evident similarity of the Decker Ferry and Cobleskill faunas by 

 the suggestion that the Cobleskill fauna recurs in the younger Decker 

 Ferry although the formations are distinct. 



He hence proposes to draw the Silurian-Devonian boundary at the top 

 of the typical Manlius and refers the Decker Ferry, the Roudout, the upper 

 beds at Manlius, and the Keyser limestone to the Devonian. 



A serious difficulty in the acceptance of this view, in the opinion of the 

 writer, is the fact that the Chonetes jerseyensis fauna has never been 

 observed above the typical Manlius of New York, while it is laiown to be 

 present in the Cobleskill.' The data upon which these views are based 

 have not been published and it is manifestly premature to discuss them 

 at this time. The author has not adequately studied the problem here 

 presented and is unable to offer any opinion as to the validity of these 

 conclusions. 



If Hartnagel's correlation of the New York sections is correct, the evi- 

 dence indicates that the Keyser member of the Helderberg fonnation is 

 equivalent to the formations between the base of the Wilbur and the top 

 of the Manlius of New York. If Ulrich's interpretation be accepted, the 

 Keyser is equivalent to the Decker Ferry, Eondout, and uppermost beds of 

 the Manlius as found in New Jersey, all of which lie above the horizon of 



^ Dr. Ulrich has kindly furnished the following comment upon the above 

 statement: " To this objection I would answer that the Keyser zones contain- 

 ing C. jerseyensis are not represented in either the Manlius, the Schoharie or 

 the Rondout sections with the possible exception of the Decker Ferry zone 

 itself, which is doubtfully identified between the cement beds (Rondout) and 

 the typical Manlius at Manlius only. At all three localities the beds between 

 the Rondout and the base of the Coeymans, or the Oriskany or Onondaga where 

 the Coeymans is absent (as at Manlius), are correlated by me with the upper 

 fourth or less of the Keyser in Maryland. C. jerseyensis was not found in the 

 doubtfully identified Decker Ferry zone at Manlius but the half hour's search I 

 gave these beds is insufficient to establish the absence of the fossil at Manlius 

 above the typical Manlius." 



