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PROCEEDINGS OF THE NATIONAL MUSEUM 



Figure 27. — Relationship of the present distribution of the subgenus Corynorhinus and the 

 maximum southward extension of Wisconsin glaclation. Plecotus townsendii, horizontal 

 shading; P. mexicayius and P. rafinesquii, vertical shading; southern limit of glaciers, 

 heavy line. 



before the advance of the ice. Probably temperate climate inhabit- 

 ants found conditions least severe in the southwest and in the extreme 

 southeast, in the region of the Carolinas and Florida which was pro- 

 tected by the Appalachian Highlands from the winds that blew off 

 the icecaps during some phases of the glacial cycle. The Gulf Coastal 

 pathway south of the ice may have been less hospitable for these forms 

 inasmuch as it was unprotected from the ice chilled winds and had 

 rivers of meltwater flowing across it. Furthermore, competition for 

 its limited niches may have been acute. 



Under these conditions, a population of Plecotus that may have 

 had a transcontinental distribution in the Yarmouth interglacial age, 

 might have been isolated into southeastern and southwestern seg- 

 ments during the ensuing Illinoian glacial age. The southwestern 

 segment included the mountains of northern and central Mexico in 

 its range. 



