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NEW YORK STATE MUSEUM 



of this division. Between this and the succeeding limestone, 

 there is an interval which is probably occupied by this mass, but 

 too deeply covered to be visible. It appears on the east side of 

 Cayuga lake, coming down to the shore. 



As will be shown later, the grayish brown mass represents the 

 Cobleskill, the covered interval the Rondout and the succeeding 

 limestone the Manlius. 



Attention was first prominently called to the section under con- 

 sideration by the late Prof. S. G. Williams, in a Note on the Lower 

 Helderherg Rocks of Cayuga Lake 1 and in a paper on u The 

 Western Extension of Eocks of Lower Helderberg Age in New 

 York published in the American Journal of Science. 2 The sec- 

 tion studied by Williams was in the vicinity of Union Springs and 

 was included between the gypsum beds of the Salina and the 

 Oriskany sandstone. From this section, having according to 

 Williams a thickness of about 65 feet, he gives a list of 26 fossils, 

 a number which were, according to the identifications, representa- 

 tives of the Coeymans limestone and the New Scotland beds. It 

 is evident, however, that Williams did not examine the upper 

 horizons of this section that lie directly beneath the Oriskany 

 sandstone, or he could hardly have failed to find a nearly typical 

 Manlius limestone fauna and thus perhaps have reached a differ- 

 ent conclusion as to the nature of the fauna about Union Springs. 

 Though Williams in his determinations of the fossil forms seems 

 to have been supported by such authorities as Hall and Whit- 

 field, there can be no longer any doubt that the fauna was not 

 properly construed in assuming any definite biologic or strati- 

 graphic relation to the Helderbergian series. 



The distinctively Siluric aspect of this fauna was first estab- 

 lished by Dr Clarke, 3 who has also given considerable attention 

 to the stratigraphy about Union Springs, which has resulted in 

 accurately determining the position in the rock series of the out- 

 crops on Frontenac island, from which the fauna of this section 

 is mainly obtained. The accompanying map showing the geo- 

 logic relations about Union Springs has been prepared by Dr 



1 6th An. Rep't. N. Y. State Geologist. 1897. p. 10-12. 



2 Ser. 3. 1886. 31 : 139-45. 



8 N. Y. State Mus. Mem. 3. 1900. p.99-101. 



