12 Bulletin 6 la 



the Cuyahoga sedlion near Cleveland, Ohio, to the Chenango 

 sedlion of the Chenango valley. The conclusions which Prof. 

 Williams reached from the study of these sedtions regarding the 

 chara(?i:er of the Portage, he expresses as follows*: "The Port- 

 age rocks and their faunas are comparatively local, belonging to 

 the central part of the area, the fauna failing in the more west- 

 ern se(ftions, and both fauna and lithologic chara(?ters are unrec- 

 ognizable east of the Cayuga secftion." 



Concerning the differences between the faunas of the Portage 

 horizon and the Genesee along the Cayuga and eastern se(5lions 

 he says,t "It is evident from the study of the secftions, that the 

 interval occupied in the Genesee sedlion by the typical Portage 

 fauna is represented in the Cayuga secftion by an entirely differ- 

 ent set of species, while still farther east in the Chenango and 

 Unadilla secflions the same interval is filled by a preliminary 

 stage of the Catskill. ' ' 



The views which Williams held of the relation of the fauna 

 of the Ithaca group to its antecedent and subsequent faunas, 

 he states as follows: "The Ithaca group of the State reports 

 contains faunas which I have defined as stages in the successive 

 modification of the Hamilton fauna. This set of faunas differs 

 from the Chemung 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. "X 



The Ithaca fauna, like the Portage, Williams considers to 

 have a limited geographical extent, being best developed in the 

 east, and blending toward the west with the Portage fauna 

 which in the western secftions entirely replaces it. The transi- 

 tion at Hornellsville from the Glyptocardia fauna of the Portage 

 directly to the lowest true Chemung fauna characflerized by 

 Orthis tioga he considers evidence that the Ithaca group has no 

 representative in the region west of there. § 



The correlation of the Upper Devonian faunas of central and 

 eastern New York with those of the more western has been at- 

 tended with considerable difficulty owing to the changes in the 

 several faunas in passing westward. In most of this region the 

 Tully limestone and Genesee shale are absent, their most eastern 



*Proc. Am. Assoc. Adv. Sci., vol. xxxiv, p. 233. 



t Ibid. 



X Ibid. 



\ Bull. U. S. Geol. Surv., No. 41, p. 30. 



