166 PROCEEDINGS OF THE NATIONAL MUSEUM vol. ho 



brown; division between colors of tip and base often not sharp; hairs 

 at posterior bases of ears frequently paler than those of other parts of 

 dorsum. Mass effect darkens with wear. Hairs of chest and belly 

 slate, gray, or brownish at base, brownish or buff at tip, the division 

 between the colors often not sharp; hairs of chin and throat like 

 remainder of underparts or with darker colored tips; hairs bordering 

 membranes with bases colored like tips. Immature like adult, except 

 darker or duller throughout. 



Size varies from medium to large for the subgenus; forearm varies 

 from medium, relative to skull length, to long; presternum with lobes 

 not expanded (ventral lobe narrower at tip than lateral lobe) (fig. 5). 

 Rostrum varies from weak and depressed to strong and not depressed ; 

 anterior nares relatively small to relatively large, and posterior 

 border rounded, or with angular shape; intermaxillary notch usually 

 relatively broad; median postpalatal process usually styliform, with 

 narrow base (sometimes triangular) ; auditory bulla averages relatively 

 large; brain case averages relatively shallow for subgenus. I^ with 

 secondary cusp varying from prominent to absent (fig. 2); P* with 

 small anterointernal cingular cusp varying from present to absent. 

 Tragus (possibly also auricle) averages relatively long; cross-ribs on 

 interfemoral membrane average 10 or more. 



Comparisons: See pages 138, 140, 142, and 151. 



Relationships: Of the three Recent species of the subgenus 

 Corynorhinus, P. townsendii has the largest geographic range and the 

 greatest environmental tolerance. Its geographic range almost spans 

 the continent from east to west and extends through 35 degrees of 

 latitude. It inhabits broadleaf deciduous forests, coniferous forests, 

 prairies, and desert scrub; cool, humid, rain forests and hot, arid, 

 deserts; coastal lowlands and high mountains; areas with great 

 annual temperature variation and areas with slight annual temperature 

 variations. 



The other species of the subgenus are much more restricted: P. 

 mexicanus to the cool, humid, highlands of northern and central 

 Mexico; P. rafinesqiiii to the warm, humid, lowlands of the south- 

 eastern United States. 



P. mexicanus and P. rafinesquii appear to be genetically stable and 

 only slightly variable, whereas P. townsendii is so variable that several 

 geographic races are recognized. P. townsendii appears to be the 

 most plastic, progressive species of the genus Plecotus. 



Remarks: Plecotus townsendii was long known only by the Colum- 

 bia River specimens upon which Cooper based his 1837 description. 

 Beginning with Harrison Allen in 1864, P. townsendii was confused by 

 aU authors with P. rafinesquii (=P. macrotis) until the two species 

 were recognized as distinct by G. M. Allen in 1916. Allen continued 



