96 STUART WELLER 



have immigrated from the north by way of the tract now occupied by 

 the fauna about James Bay, but there are few facts to support this 

 hypothesis in the known distribution of the Devonian faunas of the 

 Arctic region except the presence of several genera of fishes which 

 occur in the fauna in America and in Devonian strata in Spitzbergen. 

 The minghng of the Onondaga and Oriskany faunas in western On- 

 tario, however, suggests that this was the first point of contact between 

 the immigrant fauna and the pre-existing Oriskany, and would there- 

 fore indicate a northern origin for the fauna as a possibility. Ulrich 

 and Schuchert' have postulated a southwestern origin, and later 

 Schuchert^ has suggested a northeastern origin for the fauna through 

 the St. Lawrence Gulf and the Connecticut trough, but there seems 

 to be as little basis for either of these hypotheses as for its northern 

 origin. 



East of the Cincinnati arch the Hamilton epoch is initiated by the 

 fauna of the Marcellus shale which is evidently of Atlantic origin in so 

 far as it is not evolved from the Onondaga, but this eastern incursion 

 was of brief duration and did not penetrate to the subprovince lying 

 west of the Cincinnati arch. The Hamilton proper is introduced 

 throughout the province, both east and west of the Cincinnati arch, by 

 the appearance in the faunas of certain peculiar brachiopods which 

 are apparently of southern hemisphere origin, the most conspicuous 

 of which are Tropidoleptus carinatus and Chonetes coronatus. Aside 

 from this southern element the Hamilton fauna is in large part a 

 derivative from the subjacent Onondaga, a considerable number of 

 species being common to the Hamilton and the Onondaga, while 

 many Hamilton species are closely allied, apparently genetically, to 

 forms in the Onondaga fauna. 



In its geographic distribution the Hamilton fauna does not extend 

 as far north as the Onondaga, but it has a greater distribution south- 

 ward along the Appalachians. West of the Cincinnati arch it is clearly 

 defined in southern Illinois ; it is probably present with the Onondaga 

 in northeastern Mississippi, although data are not at hand to make a 

 definite statement to that effect, and it has been clearly recognized in 

 northern Alabama.^ 



I Rep. N. Y. State Pal, 1901, p. 652. 3 Schuchert, Am. GeoL, XXXII, 152. 

 ^ Am. GeoL, XXXII, 156. 



