DEVONIAN AND MISSISSIPPIAN FAUNAS 105 



The path of communication between the Eastern Continental 

 Province, in Onondaga time, and the Western Continental Province 

 must have been indirect, ahhough there was certainly some community 

 of origin of the faunas in the two regions. If the northern origin of the 

 Onondaga fauna, as has been suggested by the writer,^ has sufificient 

 foundation, which is perhaps doubtful, the fauna may have migrated 

 southward into two epicontinental embayments, one into the Eastern 

 Continental Province, by way of Hudson Bay and James Bay, and 

 another farther west into the Western Continental Province. The 

 mingling of the Onondaga and the lowan faunas might be accounted 

 for on this basis, since it is quite definitely recognized that the latter 

 fauna has a northwestern origin, at least in so far as North America is 

 concerned. One objection to this view is the fact that the Onondaga 

 fauna is not represented among the known faunas from the Mackenzie 

 Basin, ahhough there is sufficient room for its occurrence in some of 

 the older Devonian beds of that region which have not yet afforded 

 any fauna. A southern pathway of communication between the two 

 provinces is a possibility, although on such an hypothesis the absence 

 of the southern hemisphere element of the later Middle Devonian 

 faunas of the East is not easy to account for. 



THE NORTH AMERICAN MISSISSIPPIAN PROVINCES 



The early stages of the Mississippian period were marked by a 

 continuation of the transgression of the sea in the south and south- 

 western part of the Eastern Continental Province, which had been 

 iniiiated during Upper Devonian time, but it was extended also to the 

 northwest. Before the close of the Kinderhook epoch, the sea had 

 crossed the Kankakee peninsula and had surrounded the Ozark land 

 which became an island or was perhaps entirely submerged, and 

 had stretched away toward the Rocky Mountain land, so that the 

 earlier Eastern Continental and Interior Continental provinces were 

 merged into one great interior province with three subordinate basins 

 or subprovinces, (i) the Appalachain Basin lying between Appalachia 

 and the Cincinnati arch and extending from Michigan to Alabama, 

 (2) the Mississippi Valley basin extending westward from the Cincin- 

 nati arch and merging with the Appalachian Basin to the south, (3) 



' Jour. Geol., X, 429. 



