38-i BULLETIN OF- THE 



human agency, or whether it may not be due exclusively to the latter 

 cause. 



2. The Natural Provinces of the North American Tem- 

 perate Region * 



Before passing to the special subject of the present article, it will be 

 necessary to consider briefly the North American continent as a whole. 

 As already shown, North America embraces portions of three realms, 

 the Arctic, the North Temperate, and the Tropical. It belongs mainly, 

 however, to the North Temperate Realm, of which the temperate por- 

 tions of North America form the Western Region. Within this Region 

 may be recognized two Provinces, — an Eastern and a Western, — quite 

 distinct from each other in their general features as well as in man; 

 special characteristics. The Eastern Province is characterized by the 

 uniformity of its geographical and climatic features and by a com 

 sponding uniformity in its faunal and floral aspects. The Wester^ 

 Province, on the other hand, is characterized by the diversity of ito 

 geographical and climatic features, — different areas situated under the 

 same parallels differing greatly «n these respects, — and by the number 

 and small extent of its zoological and botanical areas, and its compara- 

 tively numerous restricted flora 1 , and fauna?. 



The Eastern Province f extends in the United States from the 

 Atlantic seaboard to the vicinity of the 100th meridian, but to the 

 northward its western boundary sweeps rapidly westward, and extends 

 to the Rocky Mountains, whilst farther northward, where it approaches 

 the Arctic Realm, it occupies the whole breadth of the continent. Its 

 ■western border is not generally abruptly defined, and is, moreover, quite 

 irregular, through its extension up the valleys of the numerous rivers 

 which enter it from the westward. According to Professor Baird, its 

 western boundary "starts on the Gulf of Mexico near the eastern bor- 

 der of Texas, perhaps between the Brazos and the Sabine, and follow- 



* The " Districts" of the North American Region, or the ontological divisions of this 

 region of the fourth rank, can be more conveniently characterized after the seve 

 fauna' have been defined, to which point in the paper their consideration i^ accordingly 

 deferred. 



t The boundaries of these two regions have been sketched with apparent accuracy 

 by Professor Baird. See American Journal of Science and Arts, 2d Series, Vol. XLI, 

 pp. 82-85,.Tan., 1666. 



