AMERICAN BATS — HANDLE Y 



115 



typical vespertilionid biillar shape, as seen in P. auritus and P. town- 

 sendii, is roughly circular. 



The postcranial skeleton is unknown in P. phyllotis and differences 

 in this respect between P. auritus and P. townsendii are few. In the 

 latter species the proximal articular surface of the radius is expanded, 

 and the presternum has the ventral lobe enlarged and the posterior 

 lobe laterally expanded (fig. 5). P. auritus has departed from the 

 usual phalangeal pattern of Plecotus and Euderma, in which the second 

 phalanx of the third digit is longer than the first (by a slight elongation 

 of the first phalanx and a considerable shortening of the second), 

 rendering not only the proportion different but the combined length 

 less (fig. 6). The calcaral keel, present in P. 'phyllotis, is lacking in 

 the other species of Plecotus. 



Hamilton (1949, p. 100) pointed out distinctions between the 

 bacula of P. rafinesquii and P. auritus (as described and figured by 

 Matthews, 1937, p. 222). However, intrageneric discrepancies of 

 similar magnitude seem also to exist among the several species of 

 Myotis, Pipistrellus , and Lasiurus as described and figured by these 

 same authors. Krutzsch and Vaughan (1955, p. 99) described the 



PLECOTUS ( COTYNORHINUS ) RAFINESQUII 

 USNM 297EI8 



PLECOTUS ( PLECOTUS ) flURITUS 

 USNM 18487 



x'lll 



V IV 



Figure 6. — Pectoral appendages of Plecotus, showing relative proportions of first and 

 second phalanges of third digit. 



