AMERICAN BATS — HANDLE Y 153 



sendii and P. mexicanus and sometimes occurs in P. t. australis and 

 P. t. pallescens. 



The median postpalatal process is triangular in shape, with a broad 

 base, in P. rajinesquii. It is normally narrower at the base and more 

 styliform in P. townsendii. In some examples of P. t. australis and 

 P. mexicanus the process is almost needle-like. The broad-based form 

 is encountered in some individuals of all races of P. tovmsendii, however. 



The intermaxillary notch of the palate is narrower posteriorly in 

 P. rajinesquii than in most individuals of P. townsendii. Likewise, 

 the anterior nares are relatively small in P. rajinesquii and have the 

 posterior border angular in outline. Geographically adjacent races of 

 P. townsendii have the nares larger and the posterior border rounded 

 in outline. The nares in the more remote P. t. townsendii and P. t. 

 australis are generally large and rounded, but in P. mexicanus and 

 P. t. pallescens they are relatively small and angular as in P. rajinesquii. 



Another characteristic of P. rajinesquii that is geographically vari- 

 able in P. townsendii is the appearance of the rostrum. In P. rajine- 

 squii the rostrum is typically weak and much depressed. On the other 

 hand, adjacent races of P. townsendii, P. t. ingens and P. t. virginianus, 

 as well as P. t. townsendii, have the rostrum strong and not depressed. 

 The rostrum usually is not so weak or depressed in P. t. australis and 

 P. t. pallescens as in P. rajinesquii. P. mexicanus, showing these 

 characters in the extreme, is similar to P. rajinesquii. 



Skeletons are not available for all of the races of either species, but 

 it appears that the presternum may have taxonomic worth. In speci- 

 mens examined, all lobes, but particularly the ventral lobe, were more 

 expanded in P. rajinesquii than in P. townsendii (fig. 5) . The presternum 

 of P. mexicanus is intermediate between these extremes. 



Relationships: Plecotus rajinesquii is the most primitive living 

 member of the subgenus Corynorhinus. It is simUar in many respects 

 P. mexicanus (see p. 143). It is more distinct from geographically 

 contiguous races of P. toionsendii {ingens and virginianus) than it is 

 from some of the geographically more remote races {pallescens and 

 townsendii) of that species. This indicates a considerable period of 

 isolation for P. rajinesquii and a subsequent extension of range to 

 bring the more progressive P. townsendii into geographical contact with 

 P. rajinesquii. Isolation for P. rajinesquii is further confirmed by the 

 fact that primitive traits (e.g., secondary cusp on I \ anterointernal 

 cingular cusp on P*, triangular shape of median postpalatal process, 

 small anterior nares and intermaxillary notch) which are constant or 

 nearly so in P. rajinesquii are normally variable in P. townsendii. 

 The coloration of P. rajinesquii, the only character separating all 

 individuals of the Recent species of the subgenus Corynorhinus, most 



