A MONOGRAPH OF THE BATS OF NORTH AMERICA. 177 



notch, and ends on tbc posterior border of the jintitragus. The anti- 

 tragus is longer than high. The conch is very deep, almost reaching 

 the shoulder. When the antitragus is renicved from its attachments 

 and turned outward the boundaries of the notch and the attachment 

 are distinctly seen. The external basal ridge joins the lowest of the 

 transverse ridgesat aright angle. The tragus is longer than wide and 

 is abruptlj^ truncate at the apex. The interauricular membrane is 

 deeply notched in the middle and furnished with a hairy tubercle on 

 either side. A rib connected this membrane to the snout directly back 

 of the muzzle. The muzzle with circular borders which are imperfectly 

 defined below, but trenchant and prorect above, where they are ob- 

 S(,'urely crenulate. In the median line a vertical ridge separates the 

 almost marginal nostrils. A sparse growth of hairs sparsely lines the 

 upper part of interior of the auricle. A delicate fringe covers the pos- 

 terior margin, including the hem. The hair of the back of the couch 

 and base of the antitragus can not be distinguished fr(mi that of the 

 side of the neck. The interauricular membrane is hairy on both dor- 

 sal and ventral surfaces ; a moderately stiff brush of forwardly directed 

 hairs i^roject from the rib above the snout. 



When the immense range of coloration in some bats is recalled, as 

 for example in Artibeiis perspicillatus, it is well to be cautious in dis- 

 tinguishing species by shades of fur only. 



Skull. — The brain case scarcely elevated above the vertex of the face. 

 Metencephalon slightly higher than the mesencephalon, and this in turn 

 but little higher than the face. A slight depression only between the 

 mesencephalon and the metencephalon. Tympanic bone not concealing 

 cochlea. The otic capsule comes to the periphery at both squamosal 

 bone and occiput. Semicircular canals filled with bone, save the supe- 

 rior, which retains a minute foramen. Anterior temi)oral ridge faintly 

 marked; sagitta barely defined; posterior temporal ridge trenchant. 

 Face vertex straight. Inner Avail of the orbit nearly flat ; anterior wall 

 not depressed or with a narrow transverse groove. Anterior nasal 

 spine with flat, thin, lateral process. The infraorbital foramen in front 

 of the second premolar. Squama at base of zygoma is indented. 



Distance from infraorbital canal to anterior nasal aperature equals 

 twice the diameter of base of canine. Hard palate extends a short dis- 

 tance beyond the last molar. Lower jaw with semilunar notch exceed- 

 ing the distance from angle to the condyle. The angle exceeds in length 

 the mesolateral diameter of condyle, and lies below the lower border of 

 the horizontal ramus. The symphysal spine, seen from in front the sym- 

 physis menti, is crested at lower half. 



The above description contrasts with Molossu.s rufus as folloAvs: The 

 short face vertex is abruptly inclined. The anterior tenq)oral crest not 

 seen, but the posterior crest and the sagitta are very large in many 

 specimens, resembling the parts as seen in NocHHo. 



Inner wall of orbit convex; anterior wall depressed. The anterior 

 441— No. 43 12 



