13 Ithaca Group 13 



outcrops being on the west side of the Chenango valley. The 

 absence of these formations leaves no definite line of division 

 between the Hamilton and the faunas above. This has led to 

 much uncertainty as to whether the bluish shales and sandstones 

 underlying the Oneonta sandstone and containing a fauna com- 

 posed of Hamilton fossils and a few Ithaca group species belong 

 in the Hamilton or above the horizon of the Genesee shale. 

 These faunas of uncertain affinities have been studied in Otsego 

 and Chemung counties by Williams, Prosser and Clarke. While 

 these careful observers agree in the main in their conclusions as 

 to the relations of the faunas of this region there are some dif- 

 ferences, and it may be worth while to summarize briefly the 

 results of their published studies. 



In his paper on the classification of the Upper Devonian,* 

 Prof. Williams describes the faunas of the Chenango and the 

 Unadilla river sedtions. The faunas above the Genesee shale in 

 these sedlions represent, according to him, five stages of the modi- 

 fied Hamilton fauna and one stage of the Chemung. The stages 

 which he recognizes are the Paracyclas lirata, A try pa reticularis, 

 Leiorhynchus globuliformis , Tropidoleptus carinatiis, Spirifer me- 

 sastrialis stages of the Hamilton followed by the Rhynchonella 

 contrafla stage of the Chemung. The nearly barren sandstones 

 and conglomerates lying above the last of these stages and in- 

 tervening between the first two are stages of the Catskill. These 

 modified stages of the Hamilton correspond to the Ithaca group 

 of the Cayuga sedtion. Williams finds no representative of the 

 Portage fauna in these se(5lions. 



Prof. Prosser has studied the same sections and has published 

 a complete list of the fossils identified by him in the Unadilla 

 sedlion.f 



In another paper % he discusses the correlation of the Upper 

 Devonian faunas of central and eastern New York. In this 

 Prosser recognizes above the typical Hamilton faunas represent- 

 ing two stages of the western sedtions, the Portage and the Ith- 

 aca group stages. The determination of the Portage stage seems 

 to be based on stratigraphic evidence. The presence of the 

 Portage in the Chenango valley is not shown by the lists of 

 fossils given since none of them are chara(5teristic of the typical 

 western Portage. The lists of fossils indicate that the typical 



*Proc. Am. Assoc. Adv. Sci., vol. xxxiv, p. 222. 

 1 1 2th Ann'l Rep't State Geol. of N. Y., pp. 1-35. 

 JAm. Jr. Sci., vol. xlvi, pp. 212-230. 



