GEOGRAPHICAL DISTRIBUTION. 73 



supposed to be relies of a glaeial fauna which formerly inhab- 

 ited the northern part of the temperate zone, and in former 

 times followed the retreat of a glacial, or arctic climate from 

 the low-lands to the Alpine summits. These patches, or out- 

 liers, of an Arctic fauna, containing however a preponderance 

 of subarctic forms, also occur in the colder parts of New 

 England. 



The subarctic fauna is spread over British North America, 

 stretching north-westerly from the interior of Labrador and the 

 northern shores of the St. Lawrence, following the course of 

 the isothermal lines which run in that direction, and north of 

 which no cereals grow. There are subarctic forms which inhabit 

 the shores of the Bay of Fundy, especially about Eastport, 

 Maine, where the fogs and cold arctic marine currents lower 

 the climate. 



Dr. J. L. Leconte, in a paper on the Coleoptera of Kansas 

 and Eastern New Mexico (Smithsonian Contributions to Knowl- 

 edge), thus subdivides the Coleopterous fauna of the United 

 States, and gives a useful map to which the reader is referred. 



"The whole region of the United States is divided by merid- 

 ional, or nearly meridional lines into three, or perhaps four, 

 &reat zoological districts, distinguished each by numerous 

 peculiar genera and species, which, with but few exceptions, do 

 not extend into the contiguous districts. The eastern one 

 of these extends from the Atlantic Ocean to the arid prairies on 

 the west of Iowa, Missouri, and Arkansas, thus embracing 

 (for convenience merely) a narrow strip near the sea-coast of 

 Texas. This narrow strip, however, belongs more properly 

 to the eastern province of the tropical zoological district of 

 Mexico. 



"The central district extends from the western limit of the 

 eastern district, perhaps to the mass of the Sierra Nevada of 

 California, including Kansas, Nebraska, Utah, New Mexico, 

 Arizona, and Texas. Except Arizona, the entomological fauna 

 of the portion of this district west of the Rocky Mountains, 

 and in fact that of the mountain region proper, is entirely un- 

 known ; and it is very probable that the region does in reality 

 constitute two districts bounded by the Rocky Mountains : and 

 the southern continuation thereof. 



