AMERICAN BATS — HANDLEY 143 



deeper brain case; shorter, weaker, and more depressed rostrum; 

 smaller auditory bullae; actually and relatively shorter maxillary 

 tooth row; and more consistently bilobed first upper incisor. There 

 is at least an indication of an accessory cusp on I^ in all specimens of 

 P. mexicamis that I have examined; few specimens of P. t. australis or 

 P. t. paUescens have even a trace of it. 



Relationships: There is a strong resemblance between P. mexi- 

 canus and P. rafinesquii. Similarities include short, weak, depressed 

 rostrum; deep brain case; bilobate first upper incisor; and possession 

 of a small anterointernal cingular cusp on P*. 



P. mexicanus differs from P. townsendii in somewhat the same man- 

 ner as does P. rafinesquii. This parallel may not be purely coinci- 

 dental. Perhaps both P. mexicanus and P. rafinesquii were isolated 

 from a common stock (of which P. townsendii is the Recent descendant) 

 at about the same time. However, P. mexicanus is not differentiated 

 from P. tovMsendii quite as well as is P. rafinesquii. This may indi- 

 cate more complete or longer isolation for P. rafinesquii, or partially 

 parallel evolution between P. mexicanus and P. townsendii. 



In coloration P. mexicanus resembles typical P. t. townsendii of the 

 Pacific Northwest. Apparently this parallel can be traced to similar 

 environmental stimulae. P. t. townsendii inhabits cool, humid, 

 coastal lowlands, and P. mexicanus inhabits cool, relatively drier 

 highlands. 



Remarks: Since 1890 it has been known that bats of the subgenus 

 Corynorhinus inhabit Mexico. The first specimen was referred by 

 J. A. Allen (1890) to Plecotus townsendii, then thought to be mono- 

 typic. Miller (1897) referred all Mexican specimens to a new race, 

 P. macrotis paUescens, restricting the name townsendii to populations 

 in the Pacific Northwest. Later, G. M. Allen (1916) referred all 

 Mexican material to a new race, P. megalotis mexicanus, restricting 

 paUescens to the relatively arid portions of the western United States. 

 Subsequent authors, with the exception of Burt (1938) for bats of 

 northern Sonora, have applied the name P. rafinesquii mexicanus to all 

 Mexican populations of the subgenus Corynorhinus. Present evi- 

 dence, however, indicates that there are in Mexico two species to 

 which the names P. townsendii and P. mexicanus apply. 



Evidence that these are distinct species has been overlooked, 

 although examples of each have been in museum collections for more 

 than 60 years. Reasons for this oversight are several: 



1. Populations of P. townsendii just north of the range of P. mexicanus in 

 Arizona converge toward P. mexicanus in size and in coloration, giving an illusion 

 of geographic intergradation between the two species. 



2. The two species are not strikingly different, although they are more distinct 

 than some species in other genera of bats, such as of Myotis. 



497256—59 4 



