DEVONIAN AND MISSISSIPPIAN FAUNAS 261 
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 mingling 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 Tvopidoleptus 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.? 
t Rep. N. Y. State Pal., 1901, p. 652. 3 Schuchert, Am. Geol., XXXII, 152. 
2 Am. Geol., XXXII, 156. 
