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PROCEEDINGS OF THE NATIONAL MUSEUM 



Tablk 2. — Comparison of external characters of the subgenera of Plecotus (Idionyc- 

 teris most generalized, Corynorhinus most specialized, Plecotus intermediate) 



features P. phyllotis is generalized in one (Pi) and is dubiously special- 

 ized in the others; P. auritus is generalized in all; and P. tovmsendii 

 is specialized in all. 



Likevrise, in cranial details specialization is greatest in P. town- 

 sendii, least in P. phyllotis (fig. 4). In the more primitive species, P. 

 phyllotis and P. auritus, the supraorbital region is sharply ridged; in 

 P. townsendii it is smoothly rounded [also in the Lower Pleistocene 

 P. crassidens; faintly ridged in the Middle Pleistocene P. (Coryno- 

 rhinus) alleganiensis]. The temporal ridges converge to form a median 

 sagittal crest in P. auritus and P. tovmsendii, but remain apart in P. 

 phyllotis and to a lesser degree in P. alleganiensis. 



