DEVONIAN AND MISSISSIPPIAN FAUNAS 93 



So long as one's observations are restricted to a limited area contained 

 entirely within a single life province, the problems are usually simple, 

 and some beds with similar lithologic characters and similar faunules 

 usually may be traced from section to section without abrupt changes. 

 However, when one's observations extend beyond the limits of a single 

 province or subprovince, the factors in correlation multiply, and fre- 

 quently the problem becomes one of extreme complexity. In solving 

 these problems the history of the faunas under consideration must be 

 diligently studied in order to determine the elements in their compo- 

 sition, the source of these elements, and their relations one to another, 

 both biologically, geographically, and geologically. The solution also 

 involves the investigation of the paleogeography of the region being 

 studied. 



One of the first considerations in connection with any correlation 

 problem is the determination of the several faunal provinces involved 

 and their geographic limits. 



NORTH AMERICAN DEVONIAN PROVINCES 



Upon the North American continent four well-defined faunal 

 provinces may be recognized in the Devonian strata. These have been 

 designated by Williams:^ (i) Eastern Border Province, (2) Eastern 

 Continental Province, (3) Interior Continental Province, and (4) 

 Western Continental Province. Although the boundary between the 

 Eastern Continental and Interior Continental provinces is now known 

 to be somewhat different from that assigned by Williams, the names 

 themselves express better than any others which have been proposed 

 the geographic relations of the provinces, and will be used here. 



The Eastern Border Province is confined to the easternmost 

 extremity of the continent, within the maritime provinces of Canada 

 and the State of Maine. The outcropping strata of the Eastern Conti- 

 nental Province extend from eastern New York westward across New 

 York and Ontario into Michigan, southwestward along the Appala- 

 chians across New Jersey, Pennsylvania, Maryland, West Virginia, 

 and Virginia, also down the Ohio Valley through Ohio, Indiana, and 

 Kentucky to southern Illinois, and southward into Tennessee, north- 

 eastern Mississippi, Alabama, and Georgia. Outliers are found in 



I Am. Jour. Sci. (3), XXXV, 51-59. 



