Prosser — Hamilton and Chemung Series, 



93 



result of the studies explained in this bulletin and later papers, Professor 

 Williams regarded the Ithaca group fauna. as coming from the eastward and 

 occurring in the midst of rocks which in western New York arc called the 

 Portage group, these being succeeded by the Chemung group. Professor 

 Williams summarized the section as follows, beginning with the Genesee slate 

 at the base of the section on Cayuga lake : 

 " 1 st. Genesee slate fauna. 



"2d. Portage group fauna, distributed through approximately 1,300 feet 

 of strata, but interrupted by the intrusion of the Ithaca fauna and several sub- 

 faunas. 1 



" 3d. Chemung fauna, occupying at least 1,200 feet of strata." 8 

 The distribution of the Ithaca fauna is indicated to some extent on a 

 chart of "Meridional Sections of the Upper Devonian Deposits of New York, 

 Pennsylvania and Ohio," by Prof. H. S. Williams, published in 1886. This 

 ] taper considers the composition of the Ithaca fauna and its relation to other 

 faunas, and the author says: "The Ithaca group of the State reports, contains 

 faunas which I have defined as stages in the successive modifications of the 

 Hamilton fauna. This set of faunas differs from the Chemung fauna in the 

 absence of several of its common and abundant species, and by presenting 

 unmistakable evidences of earlier stages in modification of species which are 

 near enough alike to be classified under the same specific name." 8 



In 1886, Professor Williams repeated his statement that the Ithaca zone 

 is separated from the lowest beds containing characteristic Chemung fossils 

 by about 600 feet of flaggy and shaly deposits which contain a few Portage 

 species. The author's opinion in reference to the relationship of the Ithaca 

 fauna being expressed as follows : " The Ithaca fauna and its equivalents are 



' Tliis mass of rocks is subdivided as follows by Professor Williams : 

 Upper Portage sandstones and shales 



L Upper Ithaca 



Middle Portage.. \ Typical Ithaca 



( Lower Ithaca 



Lower Portage sandstones ind shales. 



tioir 



100' V 450' 

 150' ) 



■. 250' 



1,300' 



See Prosser, in Transactions American Institute Mining Engineers, Vol. XVI, 1888, p. 945. 



> Bulletin United States Geological Survey, No. 3, on the " Fossil Faunas of the Upper Devonian along the meridian of 70° 

 30' from Tompkins county. N. Y., to Bradford county, Pa.," p. 20. See also statement on p. 20 that "the study of the order of 

 tbe faunas alone in this meridian furnishes strong evidence for the opinion that what I have called the Ithaca fauna, w hich was 

 characteristic of the ' Ithaca group ' of the early State geologists, is geographically a temporary fauna, preceded and followed 

 by the conditions and fauna generally regarded as belonging to the Portage group." The following year Professor Williams 

 Slid : "In the Portage group at Ithaca, as I have already shown, is a rich fauna, not equivalent to the Chemung, but inter- 

 mediate between it and the Hamilton." (Proceedings American Association Advancement of Science. Vol. XXXIII. Pt II, 

 1885, p. 423.1 



3 Proceedings American Association Advancement of Science, Vol. XXXIV, p. 233. This paragraph was condensed and quoted 

 as follows by Professor Williams in 1801: "The 'Ithaca group * contains a modified Hamilton fauna, which differs from the 

 Chemung fauna in the absence of some of its most characteristic species." (Bulletin United States Geological Survey. No. 80, 

 Correlation Papers, Devonian and Carboniferous, p. 134.) 



