CHRONOLOGIC RELATIONS OF THE TULLY FAUNA. 



497 



the inclusion of many Hamilton species which do not belong in the lime- 

 stone. 



There are about fifty genuine Tully limestone species. Of these less than 

 twenty-five are at all commou, and the other twenty-five are Hamilton species 

 which do not appear above the Tully, or are unique forms of Hamilton types. 

 Of the more or less common Tully forms fully one-half are also clearly 

 Hamilton species or their descendants, or are unique forms. 



The change in fauna which begins with the Tully limestone and makes 

 the characteristic upper Devonian fauna includes the appearance in New 

 York of at least ten or a dozen species which have closer affiuities with 

 species of the middle Devonian in Europe than with any previous species in 

 the New York series. 



The following table will illustrate this point : 



Of the ten most characteristic species of the Cuboides zone of Europe, 

 marked C i Q the above table, all are represented by closely allied forms in 

 the underlying middle Devonian of Europe ( — C)- 



LXVI— Bull. Geol. Soc. Am., Vol. 1, 1889. 



