AMERICAN BATS — ^HANDLET 129 



2. Supraorbital region sharply ridged; postorbital expansion of zygoma in middle 

 third of arch; basial pits absent; P* longer than wide; 3d commissure of M» 

 equal to or shorter than 2d ; P4 double-rooted ; muzzle glands 'slightly enlarged ; 

 anterior basal lobe of auricle complete; 2d phalanx of 3d digit shorter than 



1st phalanx Subgenus Plecotus (p. 132) 



Supraorbital region smoothly rounded or faintly ridged; post orbital ex- 

 pansion of zygoma in posterior third of arch; basial pits prominent; P* 

 wider than long; 3d commissure of M' equal to or longer than 2d; Pi single- 

 rooted; muzzle glands greatly enlarged; anterior basal lobe of auricle re- 

 duced; 2d phalanx of 3d digit longer than 1st phalanx. 



Subgenus Corynorhinus (p. 136) 



Subgenus Idionycteris Anthony 



Plecotus J. A. Allen, 1881, p. 184. (Part.) 

 Corynorhinus G. M. Allen, 1916, p. 352. (Part.) 

 Idionycteris Anthony, 1923, p. 1. 



Type species: Idionycteris mexicanus Anthony. 



Distribution: Northeastern Mexico and southwestern United 

 States (fig. 12). 



Description: Supraorbital region sharply ridged (fig. 4); temporal 

 ridges do not coalesce to form a sagittal crest; rostrum broad for a 

 Plecotus, flattened, and with pronounced middorsal concavity; brain 

 case relatively broad and shallow ; zygoma relatively thick and strong 

 in appearance, with postorbital expansion in middle third of arch; 

 median postpalatal process absent; basial pits absent; auditory bulla 

 slightly elongated in outline. 



I^ with accessory cusp (fig. 2), near base of tooth; P^ small, barely 

 exceeding cingulum of canine in height; P* wider than long; space 

 between posterointernal edge of P* and anterior edge of M^ only 

 about one-third the lingual length of P*; third commissure of M^ 

 equal to or longer than second commissure (fourth commissure may be 

 barely indicated) ; metacone of M^ fairly prominent ; Pi much larger 

 than P3 ; P4 single-rooted. 



Glandular masses on muzzle not noticeably enlarged (fig. 7) ; nostril 

 of primitive vespertilionid type, with well-defined cornu (fig. 8); 

 auricle with anterior basal lobe complete, but not prolonged beyond 

 anterior edge of auricle (fig. 9) ; accessory anterior basal lobe enlarged 

 and produced beyond edge of auricle as a "lappet"; transverse ribs 

 on auricle may or may not extend to posterior edge of auricle;^ tragus 

 relatively broad and short; second phalanx of third digit longer than 

 first phalanx (fig. 6); forearm averages relatively short; calcar keeled; 

 interfemoral membrane with 12 to 13 transverse ribs and attached 

 to tip of last caudal vertebra. 



> In the type of mexicanui the ribs fade out Indetennlnently near the posterior border, leaving this area of 

 membrane clear; In the type otphyllotis the ribs apparently end about 3 mm. from the posterior border, at 

 which point they break into a multiplicity of wrinkles which extend to the border; In USNM 302900. from 

 Arizona, the ribs definitely extend to the posterior border of the auricle. 



